Wisconsin Attorney General J.B. Van Hollen said Gov. Scott Walker must follow the federal Affordable Care Act.
The U.S. Supreme Court found the law constitutional on Thursday, but Walker, a Republican, has vowed not to implement it until after the November elections.
Walker said Thursday he would have preferred the court strike down the law, but he is holding out hope that a new president and Republican-controlled Congress will overturn it next year
In the meantime, Walker said the state will not proceed with setting up a health care exchange as is required.
"While the court says it's legal, it doesn't make it right," Walker said. "Our hope is that between now and Nov. 6, that there will be voters here and across the country who see fit to put in a president that will change that mandate against the American people."
Nearly 30 states, including Wisconsin, sued over the law, alleging it was unconstitutional. Van Hollen, a Republican, handled Wisconsin's participation in the lawsuit.
"We entered into this, as I said repeatedly, not because of health care, but because of the necessity to make sure the rule of law prevails and that federalism prevails, and that the federal government does not grow beyond the power granted to it by our founding fathers in the Constitution," Van Hollen said.
But Van Hollen said Thursday that Walker is obligated to follow the law according to its deadlines.
Asked at a news conference whether he was obligated to conform to the law, Walker responded by saying the legislation establishes multiple timelines.
Walker said the law will be a "massive tax increase on the people of Wisconsin and America."
He said the decision creates uncertainty for Wisconsin businesses and that's bad for job growth. Walker has also said businesses will be bullish about adding jobs since he won a June 5 recall election.
Wisconsin Republicans say the U.S. Supreme Court's ruling upholding most of President Barack Obama's health care law will have no immediate effect in the state aside from galvanizing the GOP going into the November elections.
The Republican leaders of the Legislature's health committees said the ruling perpetuates uncertainty for businesses, curtailing job growth, and voters will make things right in November.
Robert Kraig, the executive director of health care advocacy group Citizen Action of Wisconsin, said Walker has a moral obligation to begin the implementation process.
Wisconsin advocates of the health care law are focusing on the people it helps, particularly children and seniors, like Parris Jones.
Jones was at Access Community Health in Madison on Thursday. He said he can afford to go there thanks to Medicaid.
"I have four or five prescriptions filled per month. It's been a godsend to have 100 percent medical care and dental care. I'm on disability, so it's definitely a blessing," Jones said.
He said that, without insurance, filling his prescriptions would cost $1,000 a month.
"I think the politicians need to take the politics out of it, especially when it comes to health care of individuals, and be bigger," Jones said.
Under the law, those advocates said BadgerCare won't change. Families can choose their own primary care provider and young adults can stay on their parent's insurance until they're 26 years old.