There's no way based on that these guys should be convicted for knowingly committing a crime, which is what the law requires.
This is incorrect. Intent varies between crimes, and can vary even between the elements of a single crime. For example, burglary typically requires knowingly breaking and entering a residence, with a specific intent to commit a felony during the break-in, which is probably why that charge was dropped. I'm guessing that misdemeanor criminal trespass in Iowa requires only an intentional, knowing, or reckless trespass, or the charge wouldn't still be pending. Their lawyers seem to think the state's not going to meet that burden, or they wouldn't be going to trial, but the fact that they didn't know they were committing a crime doesn't necessarily mean they weren't committing a crime.
Thus mathematics may be defined as the subject in which we never know what we are talking about, nor whether what we are saying is true. -- Bertrand Russell