[vrwc1]

To be on the grounds of a government facility is not trespassing, which is what these men are being charged with, especially considering there were customers lined up waiting for the DMV to open who were not charged.

[Bubba Ho-Tep]

Legally speaking, however, the people waiting to do business with the DMV were there for the purposes to which the facility had been expressly dedicated, while the evangelists were not.

It's the same as if they had come onto the property of a store to proselytize. If they refused to leave, they could be arrested for trespassing while customers of the store were not.