I have registered 2 of my bikes.. They started implementing the "bike registration ordinance" last year, and the local traffic police has been starting to impound bikes they caught in the street w/o the license plates..

Anyway, several clubs protested on those license plates being "dangerous"... but it was really just an eyesore .. So we have agreed that the registration OR is good enough. So whenever I'm stopped becuase my bikes don't have plates on them, I just show the OR.. And they understand.