Since April 2009, it has been legal in Michigan for card-carrying patients to use marijuana for various ailments. But with the International Cannabis Convention coming to Pontiac, law enforcement and city government officials are concerned illegal use of marijuana and sales of smoking-related paraphernalia at the Silverdome. Edmund Kresty of the Saline-based Holistic Health and Educational Center, an event organizer, stressed all city and state laws will be followed and there will be "no sales or trading" of marijuana.