I saw that this morning. How the NFL handles this one will say a lot. Stills was charged with intimidating a participant in the legal process, a felony, as well as misdemeanor disorderly conduct and criminal trespass.
you charge onto the private home of the Kentucky AG you have to understand being arrested is a given.
You are correct. If you trespass on private property and refused to leave when requested, you can be arrested.
I'm not familiar with the Kentucky law but it appears that the charge relates to intimidating the Attorney General whose property they were trespassing on. The AG is conducting an investigation relating to a police shooting.
From what I read, Stills and the others arrested were asked to remove themselves from the private property or be subject to arrest. They chose to be arrested.
There is no first amendment right to trespass on private property. So, if you want to protest the AG's handling of the case do so on public property.