A Polish libertarian opposition leader tried to smoke a joint at parliament premises Friday as part of his campaign to legalize soft drugs, but was prevented by the house speaker. He burned marijuana incense instead.

Janusz Palikot, the leader of the Palikot Movement, announced in advance his plan to smoke pot at the parliament building, giving the speaker, Ewa Kopacz, time to organize tighter security at the compound in Warsaw. Guards and police officers were instructed not to let parliamentarians bring guests to the building...