In 2014, Vladimir Putin invaded Ukraine with uniformed soldiers who became known as the “little green men” because they didn’t wear unit insignia and refused to admit who they really were before they started shooting people.

Last week, Donald Trump invaded Portland, Ore., with his own version of “little green men.” They, too, wore uniforms without insignia and refused to say who they were before reportedly seizing lawful protesters, stuffing them in unmarked cars, and taking them away to locations they refused to disclose. Eventually, Trump admitted that he had ordered this invasion without the consent of state or local authorities, but claimed he didn’t need any.

This was illegal.

The law does not give the president general police powers. These belong to local officials who can request the assistance of state police, if necessary, to deal with protests. State police can ask the governor to send in the National Guard — state soldiers — if necessary to restore order. This is called “military assistance to civil authorities.” If the National Guard can’t restore order, the governor can ask for military assistance from the federal government, but the president cannot lawfully short-circuit the process. That’s what federalism means.

Unfortunately, we have a president who does not accept the limits of his authority. Neither does the Department of Homeland Security, the Border Patrol, the US Marshals Service, or the Federal Protective Service, all of which contributed anonymous pseudo-soldiers to this invasion. Like Putin’s soldiers in Ukraine, Trump’s “little green men” did not identify themselves as they blundered about making off with people in the night.

Nor did the US Army go to Portland. It knew better than to violate the criminal provisions of the Posse Comitatus Act of 1878 and usurp civilian law-enforcement powers. That also explains why the president deployed paramilitary forces akin to SWAT teams from civilian federal agencies.

Of course, Trump is hoping that voters are ignorant enough to believe that he can deploy “little green men” wherever he wants, like the dictator he so admires. We need to disabuse Trump of this delusion.

Chris Pyle

South Hadley

The writer is a professor emeritus at Mount Holyoke College, where he taught constitutional law before retiring last month. In 1970, as a former Army intelligence officer, he disclosed military surveillance of civilian politics and worked to end it, as a consultant to Senator Sam Ervin’s Subcommittee on Constitutional Rights, Senator Frank Church’s Select Committee on Intelligence, and the American Civil Liberties Union.

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