Seems like the post office wants to operate like a Government Agency when it is convenient, and operate like a separate private business when they would like to do otherwise. I hope Rand Paul will pull them off the eligible for Government contract list.
I can not find exactly what I was looking for, but this relates to it as far as the PO parking lot in our Federal jurisdiction area, 10th circuit out of Denver.
http://www.freerepublic.com/focus/news/3041657/posts
Ruling only applies within the district provided it does not conflict with a higher ruling. It does not apply to the entire circuit.
Currently, it conflicts with McDonald as a "longstanding prohibition". If I remember right, there's another ruling elsewhere that upholds the prohibition on Post Office property.