Whose Sovereignty Is Threatened By The US-Mexico Border? A Realist Take

For those in the realist tradition of international relations, control of territory represents the top concern for sovereign states. Territorial borders are therefore a high priority for statespeople. Maintaining a monopoly on armed force within (and defending against threats from without) those borders, is a keystone of state sovereignty. 

One of, if not the sharpest divides in living standards and economic development on the globe today is the US-Mexico border, prompting a great trend in migration northwards. Particularly in America, public discourse on the scale and disorganised nature of this migration has achieved points of convergence with heightened fears over sovereignty and border security, while being conducted with such acrimonious discourse that it takes centre stage in today’s American politics. 

These issues are nuanced and very important, on both sides of the border. Yet if a border like this is of such centrality to these states’ security, then it seems hardly likely the border’s migration questions are the total of its security implications. What is being occluded by all the smoke created from fanning the flames of the migration debate? Moreover, Mexico has limited resources relative to the US; with such asymmetry, how likely is it that the stronger power is the only one on the receiving end of security challenges from the border?

One issue highlights this well. In the US, ‘private’ gun sales by those not “engaged in the business” of selling arms are legal, devilish to trace, and can be made without background checks. Additionally, there is no way of effectively limiting the number of guns that can be purchased this way. Attempts to tighten the loopholes are being made, but it remains the case that money and guns swap hands privately and the Second Amendment is used to help ensure it becomes none of Uncle Sam’s business. Indeed, in 2005, the year after Clinton’s assault rifle ban lapsed, the Protection of Lawful Commerce in Arms Act gave legal protections to those in the gun supply chain from being liable for actions carried out with their guns. It was a legislative restatement of ‘guns don’t kill people, people do.’ 

Getting hold of guns legitimately in Mexico, on the other hand, is a tightly regulated affair. The army is the only seller, and the constitutional right to personal firearms is only “for security and legitimate defence” as determined by federal law. In other words, there is no US Second Amendment-style constitutional provision interpreted as allowing the populace virtually unrestricted access to firearms. The easiest way to arm yourself to the teeth in Mexico, then, is to rely on buying guns bought first in a legal and poorly regulated sale by a proxy in America, then have them cross the border. 

This is exactly what the cartels do. It is estimated between 100,000 and 200,000 guns have come across the border from US gun dealers, every year, since about 2011.  This is such a big problem that the Mexican government sued gun dealerships in Arizona for $10bn in 2021 for the design, marketing, promotion, and supply of paramilitary style arms they knew were destined for the cartels, thus destabilising the Mexican state.

What is interesting to a realist here is the impacts of this US-Mexican dispute on security and sovereignty. The Trump administration in February 2025 recognised some of the largest criminal gangs in Mexico – those same ones using the border-trafficked guns – as foreign terrorists. It was a bid to take stronger measures for shutting down the trafficking of drugs and people into the US, for which these gangs are also responsible. Mexican president Sheinbaum had tried to dissuade the Trump administration from this action with legal rebuffs, but these attempts mostly served as a tacit recognition of the de facto power the US has to violate Mexican sovereignty. 

What Sheinbaum knew, like many others, was that the US has something of a record – not to mention ample capabilities – for undertaking directed extrajudicial killings on foreign soil against targets on its terror list. Though in May this year things seemed more harmonious with Sheinbaum appearing to approve of heavy-handed policing tactics by US agencies, in June the US Supreme Court threw out the Mexican government’s lawsuit against the American gun companies and in August it was reported that Trump had signed a directive to use unilateral military means to target cartels in Mexico on its terror list. Later that month Trump boasted “Mexico does what we tell them to do. And Canada does what we tell them to do, because we have the two borders.”

America has past form here. In 1916, Woodrow Wilson had General Pershing lead an armed incursion into Mexico, without the consent of Congress or the Mexican government, to capture the ‘bandit’ Pancho Villa. The Mexican state was a fractured mess after its 1910 revolution, and control by the government weak. These conditions are replicated in parts of Mexico today. 

Wilson, soon to etch his name onto history as a democratic pacifist with his Fourteen Points, professed respect for his neighbour’s sovereignty but had no qualms about violating it in an armed incursion to get what the US wanted. As a realist looking at the US-Mexico border today, one can only ask: ‘what is to stop the Western hemisphere’s hegemon from reviving a play from this old book today’?

Illustrations: Will Allen/Europinion