Washington (CNN) -- A federal judge in Michigan ruled Thursday that a controversial penalty provision in the Obama administration's health care law is constitutional.
The issue, which is also before courts in Florida and Virginia, challenges the authority of Congress under the Commerce Clause to pass the requirement to purchase health insurance.
"The minimum coverage provision, which addresses economic decisions regarding health care services that everyone eventually and inevitably will need, is a reasonable means of effectuating Congress's goal," Judge George Caram Steeh said in the ruling.
Plaintiffs opposed to the Health Care Reform Act passed by Democrats in March had asked for the court to declare the whole law -- or at least the penalty provision of the act -- to be an unconstitutional tax.
Steeh disagreed and rejected the motion for an injunction against the law derisively labeled "Obamacare" by opponents.
"The decision whether to purchase insurance or to attempt to pay for health care out-of-pocket is plainly economic," the ruling said. "These decisions viewed in the aggregate have clear and direct impacts on health care providers, taxpayers and the insured population who ultimately pay for the care provided to those who go without insurance."
More legal challenges to the health care law are expected.
The most closely watched case is in Tallahassee, Florida, where several state attorneys general have joined a lawsuit against the constitutionality of the law. Legal experts say they expect the issues to ultimately end up before the U.S. Supreme Court.
Steeh was appointed to the federal bench by President Bill Clinton in 1998.
By CNN Justice Producer Terry Frieden