When former Secretary of Defense Mark Esper disclosed that President Donald Trump had privately proposed launching missile strikes against drug labs in Mexico (strikes that Trump reportedly said the U.S. should deny responsibility for) during his first term, the revelation was met with astonishment. In the subsequent years, the once fringe idea of turning the U.S. war on drugs into more of an actual shooting war has however gained traction. Indeed, during the 2024 GOP presidential primary, the candidates sought to outdo one another with proposals for U.S. military action in Mexico. With President Trump once again the commander in chief of the U.S. armed forces, military action against drug trafficking organizations in Mexico is all too plausible—including because of his administration’s recent designation of a number of drug trafficking organizations as Foreign Terrorist Organizations (FTOs) and revelations of increased U.S. aerial surveillance of drug labs in Mexico.
Such a use of force would, absent a change of circumstances, be hard to square with domestic or international law. Moreover, it would likely sabotage Trump’s own stated policy priorities relating to migration and could lead to retaliation against American citizens.
Trump and the Use of Force
After winning the 2024 election and even prior to returning the Oval Office, President Trump began publicly ruminating about potential military action against a range of targets in the western hemisphere and beyond. Although his proposals to annex Greenland, reclaim the Panama Canal, and “own” the Gaza Strip are sufficiently outlandish and resource intensive that Trump is unlikely to ever actually attempt to implement them, musings about military action in Mexico are different.
Trump’s track record on the use of force is relevant here. Although adverse to large-scale foreign military deployments in his first term, the United States under his leadership engaged in new conflicts and expanded and intensified existing ones. Trump’s prior administration turned frequently to airstrikes against terrorists (including escalating the U.S. air wars in Somalia and Afghanistan); raids by special operations forces; and crowing over the killing of “high-value targets” such as Islamic State leader Abu-Bakr al-Baghdadi who he claimed “died like a dog.” During his first term, Trump also ordered actions other presidents eschewed. For example, he directed attacks against Syria in retaliation for its use of chemical weapons in 2017 and 2018—something President Obama had refrained from in 2013 and which likely violated international, if not also domestic law.
Further, Trump also authorized the controversial drone strike in 2020 against Iranian general Qassem Soleimani—who both the Bush and Obama administrations had abstained from attacking due to serious concerns over Iranian retaliation, particularly given the U.S. military footprint within striking distance for Tehran and allied paramilitary groups. The prior designation of the Iranian Islamic Revolutionary Guard Corp (IRGC) (in which Soleimani was a senior commander) as an FTO seemed to have greased the skids bureaucratically to using other, more kinetic counterterrorism tools. Significantly, Trump appears not to have fully appreciated the risks of Iranian retaliation. He seemed taken aback by Iran’s unprecedent ballistic missile barrage at U.S. troops in Iraq—and immediately sought to deescalate the situation, including by downplaying the traumatic brain injuries Iran inflicted on U.S. troops as “headaches.”
These uses of force under Trump 1.0 may be instructive as to the President’s willingness to approve dramatic and sometimes ineffective or even heedless military action. The pattern appears to continue in the nascent second Trump administration. In early February, the Trump administration made much of U.S. airstrikes on ISIS in Somalia which included the president posting a video of the attack on social media.
Repurposing the War on Terror Playbook
It seems all too plausible that Trump would order airstrikes on Mexican drug trafficking organizations just as he had proposed to Secretary Esper—perhaps borrowing elements of the U.S. war on terror. Comments by Trump and a number of his close advisors suggest that the administration already has such a playbook in mind, with airstrikes and potentially raids by special operations forces against jihadi terrorists being repurposed for targeting another species of violent non-state actor on the territory of the United States’ southern neighbor.
While in Congress, Trump’s National Security Advisor, Mike Waltz co-introduced the AUMF Cartel, a war authorization modeled on the 2001 Authorization for Use of Military Force—the principal statutory basis for the U.S. war on terrorism for more than two decades. The proposed AUMF would have granted the president sweeping authority to use force against drug trafficking organizations in Mexico.
The second Trump administration has already begun to cast drug trafficking organizations as terrorists and hint at possibly using the tools of counter-terrorism direct action. Effective February 20, 2025, the State Department for the first time designated eight drug trafficking organizations, six of them Mexican entities, as FTOs. Although this step does not by itself provide authority for the use of force, in the past it has paved the way to military action, including the strike on Soleimani. Certainly the rhetoric from key figures close to President Trump suggests that the administration views FTO designation as a stepping stone to using force. Soon after the designations were publicly revealed, Elon Musk commented on social media that listing “means they’re eligible for drone strikes.” The Trump administration’s “border czar” Tom Homan said in November that the president was “committed to calling [the cartels] terrorist organizations and using the full might of the United States special operations to take them out.” Secretary of Defense Hegseth recently emphasized on Fox News that “all options will be on the table if we’re dealing with what are designated to be foreign terrorist organizations who are specifically targeting Americans on our border.”
The administration may have already undertaken steps to enable the use of force in Mexico if the president so decides. According to CNN, in the weeks since Trump took office there has been a significant increase in U.S. military surveillance flights along the U.S.-Mexico border, which some current and former U.S. officials worried could be part of an effort to develop targets for U.S. strikes. The New York Times has reported an increase in U.S. surveillance flights in Mexican airspace during the second Trump administration—though reportedly these operations are currently conducted with Mexican consent. More generally, the CIA under Trump 2.0 also reportedly aims to “take on a significant role fighting Mexican drug cartels.”
It is of course possible that the Trump administration’s saber rattling is simply posturing for domestic political purpose and/or with the objective of pressuring Mexico to step up its own efforts to counter drug trafficking organizations. Relatedly, the administration may be hoping that talk of U.S. military action and increased aerial surveillance persuades Mexico to increase cooperation on counter-narcotics. Indeed, National Security Advisor Waltz has referenced prior joint U.S.-Colombian counter-drug efforts as a potential model to emulate. Mexico, however, previously participated in a version of “Plan Colombia,” the Mérida Initiative beginning under former President Felipe Calderón, and it appears very unlikely the current Mexican government would agree to a repeat of “Plan Mexico.”
Weak Checks on the U.S. President Using Force
Although Article I of the Constitution assigns to Congress the power to “Declare War,” today, as a practical matter, the President would claim broad discretion to order military action against targets in Mexico—even without authorization from Congress. The notional legal guardrails on the U.S. president using force are weak—both because the rules themselves are so permissive and because it is the executive branch itself that enforces the ostensible limits. Here’s why.
Despite the express allocation of numerous war powers to Congress in the Constitution (including the Declare War clause), over time the executive branch has taken an increasingly capacious view of the president’s authority to direct the use of force under Article II of the Constitution as commander in chief, even in the absence of congressional authorization. The executive branch legal doctrine for the president’s authority to use force unilaterally is articulated in a series of legal opinions issued by the Department of Justice’s Office of Legal Counsel (OLC) which acts as something of a Supreme Court within the executive branch. According to the dominant OLC framework, whether the president may unilaterally use force depends on a two-part test. The president must be able to establish, first, that the use of force serves a national interest, and second, that the nature, scope, and duration of the anticipated hostilities will not rise to the level of “war in the constitutional sense.”
The former prong, however, has been deemed to include everything from self-defense to matters divorced from any threat of attack on the United States, like regional stabilization, rendering it close to meaningless. In the context of potential U.S. military counter narcotics operations in Mexico, it is entirely plausible that the executive branch would invoke the protection of U.S. citizens from the lethal threat of fentanyl as a national interest justifying the unilateral use of military force.
The latter prong of the test, which is a safeguard against unilateral military action that by its “nature, scope, and duration” implicates, in the executive branch’s view, Congress’s Article I power to Declare War, should in principle be more constraining. OLC has identified one particularly salient factor in reviewing whether an anticipated military operation amounts to this level of “war in the constitutional sense:” the risk of escalation. In assessing the risk of escalation, the OLC has considered whether U.S. forces would suffer or inflict substantial casualties and thus has looked closely at the presence of ground troops given “the difficulties of disengaging ground forces from situations of conflict, and the attendant risk that hostilities will escalate.”
As applied to potential military action in Mexico, it is easy to imagine OLC concluding that a campaign of airstrikes on drug trafficking organizations even if accompanied by cross-border military raids would be sufficiently limited and the risk to U.S. forces low enough that such operations would not constitute “war” in the constitutional sense. In terms of recent precedents as to what does and does not constitute “war” under OLC’s framework, the Biden administration took the position that a 15 month military campaign of airstrikes and naval actions against the Houthis in Yemen and the Red Sea was not “war” and thus did not require congressional authorization.
International law also imposes legal limits on U.S. military action and ought to pose a significant hurdle to U.S. attacks on its southern neighbor. The Mexican government is extremely unlikely to consent to U.S. military strikes or raids on its territory and has repeatedly vowed to defend its sovereignty. Absent Mexico’s consent, international law bars U.S. military action in Mexico subject to a narrow exception. Article 2(4) of the U.N. Charter prohibits “the threat or use of force against the territorial integrity or political independence of any State, or in any other manner inconsistent with the Purposes of the United Nations.” Article 51 of the Charter also provides that the treaty does “impair the inherent right of individual or collective self-defence” in the event of an armed attack.
The U.S. government might try to argue that the harm caused to U.S. citizens by the scourge of fentanyl smuggled in from Mexico entitles the United States to use force in self-defense.
The administration has emphasized that fentanyl trafficking “kills tens of thousands of Americans each year.” To underscore the threat, a recent White House factsheet stressed that “[m]ore Americans are dying from fentanyl overdoses each year than the number of American lives lost in the entirety of the Vietnam War.”
Although the traffic in fentanyl is both a foreign policy challenge and serious public health crisis, it does not constitute an “armed attack” for the purposes of Article 51 of the UN Charter. The tragic deaths of Americans from the opioid epidemic do not provide any legal basis for the use of force against Mexico in supposed self-defense. In the absence of such an armed attack, any use of force by the United States on Mexican territory—even if directed at the personnel and facilities of drug trafficking organizations—would violate the UN Charter.
Moreover, as I have previously argued, because treaties such as the UN Charter are “laws” for the purposes of the constitution’s Take Care Clause, a violation of the UN Charter would also breach the president’s duty to “take Care that the Laws be faithfully executed.”
OLC has, however, opined in 1989 memo that the president may unilaterally “override” the UN Charter’s prohibition on the use of force to launch military action in another country. Although this legal opinion does not engage with the president’s duties under the Take Care Clause and the Chair of the Senate Judiciary Committee recently called for its withdrawal, it nonetheless remains in force as the authoritative executive branch legal position. As a consequence, the president has a permission slip to use military force even if it violates the UN Charter. Indeed, during his first term Trump ordered airstrikes against Syria in 2017 and 2018 in apparent violation of Article 2(4) of the UN Charter without even attempting to justify the attacks under international law.
Not only does existing executive branch legal doctrine afford the U.S. president broad latitude to use military force even in the absence of congressional authorization and even if it would violate international law, it is generally up to the executive branch itself to judge the application of these doctrines. Congress is not bound, of course, by OLC’s opinions, but it has struggled to assert itself meaningfully on unilateral executive branch uses of force. For its part, judicial intervention is almost nonexistent.
Moreover, there are serious questions as to the current role of lawyers within the Trump administration and whether and to what extent they are constraining the actions of the White House. In a recent article raising concerns about the processes and substance of lawyering within the second Trump administration, Jack Goldsmith and Bob Bauer asked bluntly: “Is Trump getting legal advice, and, if so, from whom?”
In sum, even though U.S. military action in Mexico would almost certainly be unlawful, as a practical matter such illegality may not serve as an effective impediment.
Attacking Mexico Would be Self-Sabotage
Even if the White House convinces itself it has the legal latitude to launch attacks in Mexico or simply disregards the law entirely, the practical consequences of unilateral U.S. military action in Mexico should give the Trump administration pause. Attacking drug cartels in Mexico would not only be ineffective, it would sabotage the administration’s own stated priorities. Moreover, such a use of military force could well lead to retaliation against U.S. citizens or interests Mexico.
First off, there is little evidence indicating that U.S. strikes against drug labs or kingpins would significantly impact the quantities of fentanyl smuggled over the border. Fentanyl labs are low-tech and easily rebuilt. Scores of top traffickers have been killed or imprisoned since Mexico launched its own war on drugs in 2006. New leaders quickly emerge. Certainly, U.S. military counter-narcotic efforts in Afghanistan over the course of two decades (including bombing drug labs) yielded underwhelming results.
Although President Trump may care more about the spectacle of U.S. military action than its effectiveness (a tendency reflected in his recent posting on social media of U.S. airstrikes against ISIS in Somalia) his administration should take heed of how both the Mexican government and the cartels may retaliate in response to U.S. attacks.
U.S.-Mexican cooperation on a range of issues, including trade, law enforcement, and especially migration—would likely be collateral damage to any unilateral use of force by the United States in Mexico. Over the past decade, the Obama, Trump and Biden administrations have all leaned on Mexico to prevent migrants from reaching the U.S.-Mexico border. Mexico’s response in 2024, for example, helped reduce crossings by more than 60 percent between December 2023 and June 2024. More than any border wall, outsourcing migration enforcement to Mexico reduced the number of undocumented migrants crossing into the United States.
U.S. military action in Mexico—even under the remote possibility that the U.S. succeeded in reaching its targets without harming bystanders—would be opposed by the Mexican government. Mexico could respond by curtailing or terminating assistance in stemming the passage of migrants through its territory. Further, the unilateral bombing of drug labs or killing of narcos would also shut down the possibility of counter-narcotic cooperation with Mexico in the future.
In addition, Mexican drug cartels have generally refrained from intentionally targeting U.S. interests in Mexico as well as Americans living and vacationing in the country. Were the U.S. military to attack these drug trafficking organizations, they may well respond by retaliating against U.S. citizens and interests in an effort to coerce the U.S. government to halt its operations. Given the wide variety of U.S. economic interests in Mexico—from Wal-Mart to auto factories to U.S. owned boutique hotels—there would be broad U.S. exposure. At the very least, U.S. businesses in Mexico would likely need to invest more in more security.
Conclusion
When asked about potential use of military force in Mexico during his confirmation hearing, Secretary of State Marco Rubio noted that though that was an option at the President’s disposal, he hoped instead to cooperate with Mexico on counternarcotics. The Trump administration should indeed focus on U.S.-Mexican cooperation rather than unilateral military action south of the border. Not only would unilateral military action likely be unlawful, U.S. attacks in Mexico would sabotage the President’s own stated priorities on immigration, put U.S. citizens and interests in harm’s way in Mexico. Attacking the country’s southern neighbor out of a desire for spectacle or illusory counter-narcotics gains would not justify the almost certain adverse consequences for the United States.
Editor’s note: This piece is part of the Collection: Just Security’s Coverage of the Trump Administration’s Executive Actions