Here's the deal...time, place, and manner restrictions are permitted to prevent a person from disturbing the peace, or otherwise interfering with the normal course of business while engaging in what would otherwise be protected 1A speech, or otherwise interfering with the liberties other people enjoy. So, courts allow .gov to restrict speech in terms of the time, location, and manner, so long as those restrictions have nothing at all to do with the content of the speech. Yes, 280 can speak in public on an issue, but he cannot simply go into a .gov building with a bullhorn and start shouting, as this would interfere with the rights of others to engage in whatever business they have in that building, just as he cannot go into a residential neighborhood at 3:00 a.m. and blare his speech out of a big speaker system and avoid Disorderly Conduct issues.
As far as the issue with being armed, my advice was not that he wasn't allowed to be armed in teh building...I have no idea what the law is there...it was more along the lines of expressing concern that he may find himself in a more difficult position to defend himself on 1A grounds if he gets into a heated debate while armed. Someone sees his hand move in the wrong direction, and suddenly it's a threatining move, and he's in big trouble.