Hot news: the legalize! street rave in june does had permission to go -with all the sound systems and people- through the IJ-Tunnel to Amsterdam Noord!
they still have to talk with police, firedept, and ambulance personell which can have objections, but the permission from the council is there !
Legalize! is an organisation which creates all kind of events like demonstration pro legalizing drugs. Their biggest event is the yearly street rave and after party with 5000 people visiting.