For what it is worth, I am told that the fair is authorised by the state but run by a "Alaska State Fair Corporation". I believe the justification given by the security guards was that this was private property and that his activity was outside ordinary boundaries of a "private" event even if the LaRouche guy paid his admission.

I'm strongly on the side of political speech and support this guy's rights, but I think that this particular infringement can be blamed on the organizers of the fair, not the state or federal government.