The Heritage Foundation, correcting what it described as a “mistake” it made 21 years ago, has filed a friend of court brief opposing the federal health reform law.

The amicus brief, filed with the 11th Circuit U.S. Court of Appeals, is the first of its kind by the conservative think tank, according to a statement.

“We had no other choice,” an email from the group explained. “In its merits brief before the appeals court, the U.S. government quoted a 21-year-old statement by a Heritage Foundation policy expert supporting an individual mandate for health insurance, when Heritage’s view today is to the contrary.”

The Obama Administration used the statement in its appeal of U.S. District Judge Roger Vinson’s ruling, declaring unconstitutional the individual mandate in the Patient Protection and Affordable Care Act, the landmark legislation passed in March 2010. The Florida case, one of two where the law was ruled unconstitutional, has been joined by 26 states, all opposing the federal law. Several other federal judges have ruled the law constitutional, which all but guarantees an eventual U.S. Supreme Court ruling on the law, according to legal experts.

More than 20 challenges to the law have been filed in federal courts.

“Over 21 years ago, Heritage analysts initially (and mistakenly) considered the idea of a limited individual mandate coupled with appropriate tax incentives as a favorable answer to the ‘free rider’ problem,” the group said, referring to citizens who do not buy personal health insurance knowing that, in the event of illness or injury, the government will ensure they get the necessary medical care.  “Of course, even that limited and qualified position did not demonstrate support for an unqualified individual mandate as structured in the Obamacare statute.”

The Heritage Foundation said it believes that health insurance individual mandates will fail and are bad public policy; and that the federal government’s attempt to force private citizens to purchase health insurance in the law is unconstitutional.