[MineralMan]

I suppose that whoever owns the vehicle can determine what does and does not go on that vehicle.

[StonyBurk]

True enough--as is equally true anyone wishing to express their utter disgust at the anti-American activities on campus have a Constitutional right to free expression.

[Sloth]

I suppose that whoever owns the vehicle can determine what does and does not go on that vehicle.

It would seem that the vehicle is owned by the people of the State of Oregon.