The activists, ranging in age from 16 to 80, were arrested during an April protest at the airport. The group, led by the American Civil Liberties Union, was trying to deliver citizens' arrests to Aero Contractors.
The ACLU believes the company works for the CIA, hauling terrorism suspects to secret locations without due process.
The judge said Thursday there was not enough evidence against five of the activists, so he found them not guilty. However, the other three activists testified against the judge's advice. The judge said their own testimony incriminated them.
All sentences are suspended provided they do not go back onto the property, but all three have appealed the judge's decision.