it's the first time i've heard that there actually is a law against foreigners who arrive on tourist visas taking part in protest rallies. foreign girls from peta protest naked in front of zoos many times and i don't think they get arrested.

this became a big issue because he was a foreigner who behaved horribly to a terribly exhausted police officer who wasn't even violent to the protesters.

he probably didn't get arrested before that because the immigration officials were lazy and decided to just wait for him at the airport when he's about to leave.