Many bridges in the state have been covered for years in flags and signs of various kinds. Now there are new ones on bridges over Route 128 in the Lexington area. There are flags and signs saying “America! United we stand, divided we fall.” That’s a fine sentiment, but what gives people the right to use public property for their political messages? Are they open to anyone? Can I put up signs criticizing Donald Trump? Can I put up signs criticizing Gov. Baker? If not, why not? I know there’s no advantage to any legislator in pursuing such questions, but why is this allowed to continue?