This from today's Freep

When will marijuana be legal?
Ten days after the election results are certified, which should be by early December. But marijuana won't be commercially available for sale until probably early 2020, in part because the state must still put regulations in place and issue licenses for recreational sales. “It's not going to be an earth-shattering change,” said Jeffrey Hank, the East Lansing attorney who was one of the leaders of the effort to get the legalization question on the ballot. But after certification, “adults will no longer be arrested for simple possession and use of marijuana.”
Can I smoke marijuana in public?
Tuesday's vote is definitely not a free pass to get high with impunity. “There is no public consumption and no driving under the influence and there will be no commercial sales until businesses are licensed and approved,” said Josh Hovey, spokesman for the Coalition to Regulate Marijuana like Alcohol. Police will still be able to arrest people they suspect are driving under the influence of marijuana or if they're lighting up in public. Michigan State Police and other police organizations haven't yet worked out how their enforcement procedures will change with the legalization.