The military installation isn't open and intended for general public use. For all intents and purposes, it's private property. Controls and legalities are different on private property. You, as a property owner, can tell anyone to stay off your property. No one should be there without your permission and / or blessing. Such control extends beyond a citizen's private property to corporate private property. I worked security at an apartment complex and, as an agent of the property management company, I exercised their will to keep non-residents off the property at certain times. If a non-resident was encountered then they were identified and asked about their business on that PRIVATE property. Depending on their answer they were allowed to continue or they were sent on their way.
Does the government of Washington DC contend that the entire city is private property? I think that's a bit unrealistic and untrue if they do. If not, then how do they justify robbing free American citizens of the ability to travel on a public roadway? My better question is why hasn't anyone they've stopped sued them for violating their Civil Rights?
I greatly appreciate the intent and motivation of the Washington DC police department. In this case, however, I have to wonder if their actions haven't traded Constitutional value for the convenience of easy law enforcement.
What do you think?