DETROIT — A federal judge in Detroit on Thursday upheld key provisions of President Barack Obama's landmark health care reform law.

In a 20-page decision, U.S. District Judge George Steeh refused to issue an injunction to halt preparations for putting federal health care reforms into full effect in 2014. Steeh also dismissed the major points of the suit — requiring Americans to buy health insurance and penalizing those who don't.

Steeh is the first judge nationwide to rule on a suit claiming Congress exceeded its authority by imposing the requirements. Congress passed the Affordable Care Act in March.

The Thomas More Law Center, an Ann Arbor, Mich.-based Christian legal group that sued along with four plaintiffs, said it plans to appeal the decision.

"I think it's important that this decision be reversed to prevent Congress from overreaching the way it did in passing the original mandate," said law center attorney Robert Muise. He predicted the case will wind up before the U.S. Supreme Court. His clients opposed being forced to buy health insurance.

Nationwide, several dozen lawsuits have been filed to stop the reforms. Michigan Attorney General Mike Cox and his counterparts in 19 other states brought one of the challenges, which is set for oral arguments Dec. 16 in Florida, according to Cox spokeswoman Joy Yearout.

The attorneys general's suit argues the federal government can't force people to buy a product merely because they are U.S. citizens. But government lawyers say Congress has regulated interstate commerce for 200 years and once required men to buy muskets and ammunition.

Marjorie Mitchell, executive director of the Michigan Universal Health Care Network, said Steeh's ruling "gives me some hope."