That is exactly what I thought.....to do otherwise, could subject Amtrak to some unwanted litigation......Amtrak does not have a Do Not Travel list like the airlines do.
Amtrak cannot permanently ban anyone without "due process", which means tried, convicted and sentenced including a court order banning them from traveling by Amtrak train.
It's my understanding that Amtrak rarely pursues this to the end thus it's pretty rare.