ICE does interior enforcement too. I suspect these are not their regular uniforms. I am surprised they are not U. S. Marshals. That would seem to be the unit to defend these federal facilities. Did they duck out on this one?
They are their regular tactical uniforms. As for the US Marshals they are a very small agency and there simple aren't enough of them.
The Federal Protective Police (part of DHS) have primary responsibility for protecting federal property but they can ask for assistance from other federal agencies when they need it.
U S Marshals are quite short handed. Goes back to ‘08.