Looks like it was vetoed.
Reason given for the veto is:
"In his veto letter, sent this afternoon to the Michigan Legislature, Synder said his decision to strike down the bill surrounded its failure to allow those public entities to opt out of the concealed carry provisions. "Unfortunately, the bill did not allow schools, public day care centers, or public hospitals to prohibit persons from carrying concealed weapons on their premises," said Snyder in his veto letter. "For that reason, I am vetoing Senate Bill 59."