TALLAHASSEE, Fla. - Attorneys general from 13 states sued the federal government Tuesday, claiming the landmark health care overhaul is unconstitutional just seven minutes after President Barack Obama signed it into law.

The lawsuit was filed in Pensacola after the Democratic president signed the bill the House passed Sunday night.

"The Constitution nowhere authorizes the United States to mandate, either directly or under threat of penalty, that all citizens and legal residents have qualifying health care coverage," the lawsuit says.

Legal experts say it has little chance of succeeding because, under the Constitution, federal laws trump state laws.

Florida Attorney General Bill McCollum is taking the lead and is joined by attorneys general from South Carolina, Nebraska, Texas, Michigan, Utah, Pennsylvania, Alabama, South Dakota, Idaho, Washington, Colorado and Louisiana. All are Republicans except James "Buddy" Caldwell of Louisiana, who is a Democrat.

Some states are considering separate lawsuits - Virginia filed its own Tuesday - and still others may join the multistate suit. In Michigan, the Thomas More Law Center of Ann Arbor, a Christian legal advocacy group, sued on behalf of itself and four people it says don't have private health insurance and object to being told they have to purchase it.

McCollum, who is running for governor, has pushed the 13-state lawsuit for several weeks, asking other GOP attorneys general to join him. He says the federal government cannot constitutionally require people to get health coverage and argues the bill will cause "substantial harm and financial burden" to the states.

The lawsuit claims the bill violates the 10th Amendment, which says the federal government has no authority beyond the powers granted to it under the Constitution, by forcing the states to carry out its provisions but not reimbursing them for the costs.

It also says the states can't afford the new law. Using Florida as an example, the lawsuit says the overhaul will add almost 1.3 million people to the state's Medicaid rolls and cost the state an additional $150 million in 2014, growing to $1 billion a year by 2019.

South Carolina Attorney General Henry McMaster, who is also running for governor in his state, said Tuesday the lawsuit was necessary to protect his state's sovereignty.

"A legal challenge by the states appears to be the only hope of protecting the American people from this unprecedented attack on our system of government," he said.

But Lawrence Friedman, a professor who teaches constitutional law at the New England School of Law in Boston, said before the suit was filed that it has little chance of success. He said he can't imagine a scenario where a judge would stop implementation of the health care bill.

Some states are also looking at other ways to avoid participating in the overhaul. Virginia and Idaho have passed legislation aimed at blocking the bill's insurance requirement from taking effect, and the Republican-led Legislature in Florida is trying to put a constitutional amendment on the ballot to ask voters to exempt the state from the federal law's requirements. At least 60 percent of voters would have to approve.

Under the bill, starting in six months, health insurance companies would be required to keep young adults as beneficiaries on their parents' plans until they turn 26, and companies would no longer be allowed to deny coverage to sick children.

Other changes would not kick in until 2014.

That's when most Americans will for the first time be required to carry health insurance - either through an employer or government program or by buying it themselves. Those who refuse will face tax penalties.

"This is the first time in American history where American citizens will be forced to buy a particular good or service," said Nebraska Attorney General Jon Bruning, explaining why his state joined the lawsuit.

Tax credits to help pay for premiums also will start flowing to middle-class working families with incomes up to $88,000 a year, and Medicaid will be expanded to cover more low-income people.

No Republicans in the U.S. House or Senate voted for the bill.