By KATIE KULL, Associated Press

JEFFERSON CITY, Mo. (AP) — They city of St. Louis will proceed with a minimum wage increase after the Missouri Supreme Court on Tuesday struck down a state wage law on procedural grounds.

The court's opinion, written by Judge Laura Denvir Stith, says a 1998 law prohibiting some cities from creating their own minimum wages is unconstitutional because it was passed as part of a bill with a different subject matter.

The Supreme Court's ruling also overturned a trial court's decision that local minimum wages were prohibited by a pair of state laws setting the state minimum wage and limiting local ordinances.

"Plaintiffs are incorrect that the Missouri minimum wage law is an affirmative authorization to pay no more than the state minimum wage," the Tuesday court opinion said. "... (The minimum wage) simply sets a floor below which an employee cannot be paid."

The unanimous decision effectively reinstates a 2015 St. Louis ordinance that sought to raise the minimum wage to $10 an hour in 2017 and $11 an hour by 2018.

Missouri's minimum wage is currently $7.70 an hour.

St. Louis Mayor Francis Slay said in an emailed statement that he will give businesses a "reasonable grace period" to comply with the law. Those who do not comply will be prosecuted in municipal court, he said.

The ruling will likely not apply to other cities. That's because of a separate state law that bars local minimum wages that weren't already in place by Aug. 28, 2015 — the day the St. Louis ordinance took effect. That law was not impacted by Tuesday's decision.

Missouri Chamber of Commerce and Industry President Dan Mehan said in a statement that the court "misinterpreted legislative intent" on minimum wage laws. Mehan said issues such as wages and paid leave should be decided through a statewide approach and the Missouri General Assembly, "not on the whim of this or that local ordinance."

A legal debate over the 1998 law started in 2000 when St. Louis passed a ballot initiative requiring a "living wage" to be paid to employees of any entity with a city contract of at least $50,000, or any entity receiving at least $100,000 in economic development incentives from the city.

The local law was challenged in court by businesses and other opponents.

A St. Louis circuit judge struck down the living wage ordinance on several grounds, in part because it was so vague. But the judge also raised concerns about the constitutionality of the 1998 law. The Supreme Court dismissed an appeal because the city's ordinance had already been overturned.

In November 2015, St. Louis Circuit Judge Steven Ohmer struck down the St. Louis ordinance. He said the local minimum wage was prohibited under two other existing laws — one setting Missouri's state minimum wage, and another mandating that local ordinances conform to state law. However, he did say the 1998 law was procedurally unconstitutional.

His ruling came just hours before the first, 60-cent increase from the St. Louis ordinance was supposed to take effect.