Most Michigan residents will find their work places, restaurants and bars smoke-free beginning May 1 now that Gov. Jennifer Granholm has signed a smoking ban into law.

But the new law could still face a court challenge, with bars and restaurants affected by the ban arguing it's discriminatory to exempt three Detroit casinos.

The Democratic governor signed the measure Friday at Michigan Brewing Co., a downtown Lansing brew pub that already bans smoking. She said the pub's experience with going smoke-free shows that "you can make a go of it and be very successful, and be healthy as well."

Dozens of smoking ban advocates crowded into the restaurant, erupting into loud cheers when Granholm announced after signing the bill, "It's done!"

"This is the greatest gift we could give the citizens of Michigan because it keeps on giving," said state Sen. Ron Jelinek, a Three Oaks Republican who helped craft the compromise that became law.