Anony Mous,
There's no "IF" here. Joint sessions of Congress normally happen twice a year (State of the Union address and Convention of the Electoral College) and the Capitol Building and grounds are closed on these occasions.
Constitution and Independance Avenues are closed. 1st and 3rd Streets are closed. Mobile barricades with "Area Closed" signs mark the boundaries of the protective zone established by the Secret Service.
Crossing into the protective zone, even inadvertently, is trespass although an angry shout from a police officer is about all that would normally happen, provided you complied with the order to leave. If you refuse to comply, it's no longer a misdemeanor. If you have a weapon in your possession, it was never a misdemeanor.
Like I said, I'm sympathetic to J6 defendants who were denied due process and I'm also sympathetic to any who did not realize the seriousness of what they were doing, although I think you would have to be low grade moron to fall into that category.