Mine isn't a legal definition, but a practical one:

You have infantry and armoured vehicles patrolling the streets and securing "critical points", with civilian law enforcement either out of the picture or reduced to a secondary force. And if someone in uniform decides to arrest you, they do- if they decide you are resisting, you are. And the courts don't get a hell of a lot to say about it until MAYBE long after.

Remember, cops aren't soldiers; soldiers aren't cops. Soldiers do not know nor care a whole lot about the law, only maintaining order on the principle that when things are out of order they are in danger. And no offense to anyone here, but I've known a lot of Gaurdies (who would be among the mostly likely troops called out for ML) who I don't trust with a loaded baseball bat, much less a rifle. If seeing infantry on the street of an American town doesn't scare the poop out of you, it should.