[Bruce Campbells Chin]

In this case, the defense against trespassing isn’t ignorance of the law, but rather ignorance of the fact that they weren’t permitted to be where they were. And that is a legally valid potential defense.

[Gay State Conservative]

I've seen it written that some...if not many...people who entered government buildings did so in a calm,orderly fashion...almost as if if they were entering on an ordinary day as many tourists routinely do.

To the extent that that might be true it seems that they had no reason to believe they were trespassing.