Just seven minutes after President Barack Obama signed the landmark health care overhaul into law on Tuesday, attorneys general from Michigan and 12 other states sued the federal government, claiming it is unconstitutional.

In Ann Arbor, the Thomas More Law Center, a Christian legal advocacy group, filed its own lawsuit 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.

The multistate lawsuit was filed in Pensacola after the Democratic president signed the 10-year, $938 billion bill the House passed on 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.

The Thomas More Law Center filed its suit in federal court in Detroit. The center said it alleges that Congress had no authority to pass the law and that Congress violated the 10th Amendment by usurping the power reserved for the states and the people.

At the heart of all of these lawsuits is the point that in no time in the history of the United States has Congress decided to force individuals to purchase a commercial product under the penalty of law, said Robert Muise, senior trial counsel at the center.

"Really this is a challenge to the power of the federal government and I think this is a case and an issue that the Supreme Court will decide because this is a fundamental issue of how broad the federal goverment's powers are," Muise said.

The center's lawsuit also alleges the law forces private citizens to fund abortion, and that doing so violates the First Amendment. "This bill is going to be used to use public funds forced from private individuals to fund abortion," he said.

Groups who oppose abortion have differed in their opinions over what the health care bill's impact would be. Those who oppose it, including the United States Conference of Catholic Bishops, have said it did not go far enough to limit the use of federal subsidies to pay for insurance policies that cover abortion, according to an article in the New York Times.

Florida Attorney General Bill McCollum is taking the lead on the multistate lawsuit 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, a Democrat.

Some states are considering separate lawsuits - Virginia filed its own Tuesday - and still others may join the multistate suit.

McCollum, who is running for governor, 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.

"We simply cannot afford to do the things in this bill that we're mandated to do," McCollum said at a press conference after filing the suit. He said the Medicaid expansion in Florida will cost $1.6 billion.

"That's not possible or practical to do in our state," he said. "It's not realistic, it's not right, and it's very, very wrong."

South Carolina Attorney General Henry McMaster, who is also running for governor, said 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.

Still, McCollum said he expects the U.S. Supreme Court will eventually decide if the overhaul is constitutional.

"This is not lawful," he said. "It may have passed Congress, but there are three branches of government."

Some states are looking at other ways to avoid participating. Virginia and Idaho have passed legislation aimed at blocking requirements in the bill, 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, who is also president of the National Association of Attorneys General, 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.

Associated Press Writer Meg Kinnard in Columbia, S.C., David Runk in Detroit and Josh Funk in Omaha, Neb., contributed to this report. Tina Reed contributed to this report.