President Donald Trump has already deployed the military in two major American cities and, when challenged in court, he has (mostly) prevailed. It’s no surprise that a man who is so easily emboldened now vows to flex his executive power in major urban centers across the country. Leading Democrats have voiced concern that the President’s recent moves in Washington, D.C. and California are merely test cases, presaging inevitable attempts to bigfoot other cities. 

But, thus far, Trump has activated the National Guard based on invocations of obscure laws, limited in operational scope and geographic reach. His promised forays into Chicago, Baltimore, and New York – and god knows where else, eventually – will face an entirely different set of legal obstacles, and won’t go as smoothly for him.

Earlier in August, Trump activated the National Guard in Washington, D.C. But D.C. is constitutionally unique. While governors control National Guard troops in their states (with narrow exceptions, which we’ll consider shortly), the president holds unilateral power over the National Guard in D.C.; as the Guard explains on its website, “The D.C. National Guard is the only National Guard unit, out of all of the 54 states and territories, which reports only to the President.” There’s a fair debate about whether Trump’s deployment was a sound policy response to concerns about violent crime in the nation’s capital, but it most certainly was legal. In fact, when the District of Columbia attorney general sued Trump over the D.C. takeover, he didn’t even contest the President’s authority over the National Guard.  

Trump relied on different – but also quite narrow – legal authority to call out the National Guard in California. As protests spread in Los Angeles and elsewhere over the administration’s deportation policies and tactics, the President invoked the Insurrection Act to activate the California National Guard. Under that law – which was last utilized over 30 years ago, during the 1992 Los Angeles riots – the President can usurp the governor’s power over the Guard in rare cases of foreign invasion, rebellion, or when “the President is unable with the regular forces to execute the laws of the United States.” 

Governor Gavin Newsom sued, and a federal district court judge rejected Trump’s action. But the (famously liberal) Ninth Circuit Court of Appeals, in a unanimous three-judge decision, reversed the trial-level judge and ruled that Trump was within his legal rights. Importantly, the Court of Appeals rejected Trump’s argument that the determination to invoke the Insurrection Act and mobilize the California National Guard was his alone, entirely unreviewable by the federal courts. But the Ninth Circuit ruled that the courts “must be highly deferential” to the president. And the appellate panel upheld Trump’s determination that deployment of the National Guard was necessary to enforce federal law, given specific evidence in the record that federal buildings had been damaged and federal officers had been assaulted.  

Trump surely will try to emulate this approach if and when he seeks to activate the National Guard in Illinois, Maryland, New York, and elsewhere. Witness, for example, the President’s recent executive order that calls for National Guard troops to be “trained and ready to assist in quelling civil disturbances nationwide”  and available as a “quick reaction force for rapid nationwide deployment when circumstances warrant” – a plain precursor of expanding deployments to come. 

But Trump will face a far steeper legal climb. He cited the anti-ICE protests in Los Angeles to justify his use of the Insurrection Act and its allowance of presidential deployment of military forces necessary to execute federal laws and protect federal interests. But there are no such protests ongoing in other major American cities, leaving Trump without any easy legal hook. 

Instead, watch for Trump to point to crime statistics and claim some generalized public safety emergency. But that’s a legally dubious gambit. In its opinion upholding the California deployment, the Ninth Circuit pointed to concrete, uncontested examples of protesters assaulting and causing harm to federal employees and buildings. It’s doubtful, by contrast, that a generalized claim of “Everyone’s in danger because of crime rates” will do the trick. I suspect it won’t; otherwise, presidential authority to mobilize the National Guard in the states would be virtually unlimited. Any president can find some alarming statistic or trend in virtually any city at nearly any time. The bar for a presidential activation of the National Guard is supposed to be high – though it’s perhaps lower than we would’ve imagined, given the Ninth Circuit’s decision – but it does require some specific justification, and not just broad calls for alarm.

Beyond the National Guard, Trump also has signalled an intent to take over local urban police departments. He did just that with the Metro Police Department in Washington, D.C. (D.C. is policed by a latticework of federal and local agencies; the Metro PD handles the day-to-day street policing, much like the NYPD or the LAPD.) 

But, again, D.C. is legally unique. An obscure provision of the D.C. Home Rule Act empowers the president to instruct the mayor to deploy the Metro PD as necessary when the president “determines that special conditions of an emergency nature exist.” The D.C. attorney general’s lawsuit challenging Trump’s takeover largely went the President’s way. The judge prohibited Trump from displacing the Metro PD’s pre-existing leadership, but permitted the President to issue orders to the police department, so long as they are routed through the mayor. 

But here’s the problem for Trump: No other city has a remotely similar law. In fact, the president is essentially powerless to usurp command of local police forces, which operate on state and local authority. Trump can try to influence local policing through federal funding or political persuasion, but he simply cannot forcibly take over any other police department like he can in D.C.  

Trump’s intentions are plain. He wants to exercise maximum power over policing in the nation’s cities – primarily or exclusively those controlled by Democratic mayors – and he seeks to reap the political benefits of his blunt-force clean-up-the-streets stance. (New polling shows that 55 percent of respondents favor the use of the National Guard to assist local police while only 37 percent disapprove.) Whatever one might think of the crimefighting efficacy of the President’s approach, thus far he’s generally operated within the law, relying on a handful of obscure carveouts that apply narrowly to Washington, D.C. and the California protests. But as Trump steps out into America’s major urban centers beyond the capital and the coast, he’ll find the legal terrain far less forgiving.