A federal judge in Michigan on Thursday dismissed one of more than 15 legal challenges to the new health care law, becoming the first to rule that the law is constitutional.

Two other cases with higher profiles, one in Florida and one in Virginia, are headed toward hearings on the issues that were decided in Michigan. The central question, which may ultimately fall to the Supreme Court, is whether the Commerce Clause of the Constitution gives Congress the authority to require citizens to obtain a commercial product, namely health insurance.

Starting in 2014, the law will require most Americans to obtain health insurance, while prohibiting insurers from denying coverage to those with pre-existing conditions.

Judge George C. Steeh of Federal District Court in Detroit ruled that choosing not to obtain insurance qualified as an example of “activities that substantially affect interstate commerce.” That is the standard set by the Supreme Court for Congress’s compliance with the Commerce Clause.