Religion

There are plenty of things that the federal government can do on federal property... for example I was stopped and searched for drugs in my car frequently, you can forget OSHA regulations, etc.

However, at the gate to the facility there was a large painted red stripe right across the pavement. The demarcation line for the federal property. The feds absolutely cannot control what happens outside that line ( and usually the fence or building perimeter that defines the extent of federal property ). Seriously.

If I ware the faith leaders holding services outside the facility... I would ask the local and state police to come with ( and plenty of lawyers ) and ignore any requests from CBP or ICE. They cannot control what happens on non-federal land. The most they can do is try to arrest someone for "impeding federal law enforcement"... so do not block their cars from entering or exiting... but you can stand on the sidewalk or open field and pray pray pray... loudly if you so desire.