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A host of Arizona lawmakers joined a conservative watchdog group Thursday in filing a 78-page lawsuit challenging the federal health care overhaul, becoming the latest party to enter the growing fight against the law at the local level.

The lawsuit, filed in U.S. District Court in Phoenix by the Goldwater Institute and Arizona representatives, takes aim at several key provisions in the health care law, focusing primarily -- as most challenges have -- on the requirement to purchase health insurance coverage.

"Congress simply does not have the power under the 'commerce clause' to require an individual mandate. This is the first time that Congress has attempted to compel individuals to buy a private product," said Clint Bolick, an attorney in the case.

Bolick called the law, which won't go into full effect until 2014, unconstitutional and "one of the most sweeping invasions of individual liberty and state sovereignty" in history.

The courts will be the judge of that. But in the considerable window before the individual mandate kicks in, dozens of states are coming at the law from all sides to make their case against it.

Missouri made waves last week when 71 percent of state voters backed a ballot measure to block the federal government from requiring people to buy health insurance. Oklahoma and Arizona are expected to have similar questions on their ballots in November, though theirs propose constitutional amendments. Florida lawmakers were pushing a similar measure, but it was removed from the ballot following a ruling from the state Supreme Court.

On top of that, five state legislatures have enacted or signed statutes to limit or block provisions of the health care law. According to the National Conference of State Legislatures, at least 40 states legislatures have proposed laws challenging the federal policy.

And the lawsuits keep piling up. Apart from the suit announced Thursday, the state of Arizona was one of the approximately 20 states party to the sprawling court challenge led by Florida Attorney General Bill McCollum. And Missouri Lt. Gov. Peter Kinder joined three other plaintiffs in filing another court challenge.

Those challenges may have gotten a morale boost last week when a separate challenge, led by Virginia Attorney General Ken Cuccinelli, was allowed to proceed in U.S. District Court.

Judge Henry Hudson ruled last Monday that he would allow the suit to proceed, saying no court has ever ruled on whether it's constitutional to require Americans to purchase a product.

"While this case raises a host of complex constitutional issues, all seem to distill to the single question of whether or not Congress has the power to regulate -- and tax -- a citizen's decision not to participate in interstate commerce," Hudson wrote in a 32-page decision.

Cuccinelli argues the health law conflicts with Virginia's legislation exempting state residents from the coverage requirement. Cuccinelli also argues that the law violates the Constitution's Commerce Clause.

The Commerce Clause allows the U.S. government to regulate economic activity. But opponents claim that it's not economic activity when someone chooses to refrain from participating in commerce.

The U.S. government argued that everyone will need medical services at some point in their life and therefore is either a "current or future participation in the health care market," and therefore subject to taxation.

"We do not leave people to die at the emergency room door -- whether they have insurance or not. ... Congress has the authority under the Commerce Clause to address that cost-shifting burdening the interstate market for health care," argued the brief filed by the Justice Department on behalf of Health and Human Services Department.

Supporters of the law said the decision last week was merely procedural, but the law will be proven constitutional when it gets to a hearing on the content.

"This case is really a politically motivated ploy aimed at diverting attention from the many benefits of the new law," said Ron Pollack, executive director of Families USA.

White House Press Secretary Robert Gibbs, defending the individual mandate, said last week that "you have to have everybody in the system" in order to bring down health care costs.

Some consider the ballot initiatives and state laws to be symbolic protests since federal law generally trumps state law.

But Bolick said that view is flawed -- he said that's only true if the federal law is one Congress has the authority to enact, does not violate individual constitutional rights and does not infringe on power reserved for the states.

Bolick said the health care law "flunks" all three of those conditions and predicted good odds should any challenge eventually reach the "pro-federalism" Supreme Court.

Other lawmakers supporting the Arizona lawsuit include Republican Reps. Jeff Flake, Trent Franks and John Shadegg, as well as a number of state lawmakers.