Ummm...ok
I didn't even need to go to
reductio to reach
absurdum. Are you certain you want to use this scenario?
OK, so based solely on the scenario you provided:
Lets say we had advance warning of what planes were gonna hit DC NY and Pennsylvania but not the exact building or neighborhood.It's September 11, 2001. Hijackers have taken over 4 airliners.
The Federal government knows (through unspecified means which violate the laws of space and time) that planes will strike unknown target or targets somewhere in the greater New York City metropolitan area, and somewhere in the greater Washington DC metropolitan area; and the passengers of one airliner will at some point in the immediate future fight back, and the plane will crash
somewhere in the state of Pennsylvania.
The Federal government communicates this knowledge to the mayors of all affected cities, and the governor of Pennsylvania, who send the police out.
Cops race into the neighborhoods or the office buildings in those areas were the planes are most likely to hit and start telling people to "get out".The government can only do two things:
Ask the people to leave their homes and businesses (with the option to say "no"), or
order them to do so (with the force of the government behind that order, including the power to arrest or use deadly force). Since you used the words
telling people to "get out",
asking is not on the table.
So, the mayors and Governor identify "most likely" targets, and direct their law enforcement agencies to order evacuation of neighborhoods and particular buildings, based on their assessment of "most likely" targets, but nothing more specific.
A citizen refuses to evacuate: what then? If the police shoot him, arrest him, or forcibly remove him based only on the scenario you provided, they have violated his civil rights.