Alaska Gov. Sean Parnell said Thursday he will not implement President Obama's health care overhaul because a federal judge in Florida ruled it unconstitutional, prompting the Justice Department to take the case back to the judge.

Attorneys for the Obama administration filed what is known as a motion to clarify late Thursday, asking U.S. District Judge Roger Vinson to make clear that states cannot ignore the new health care law while his ruling is being appealed.

Vinson ruled Jan. 31 that Obama's entire health care overhaul law is unconstitutional. That placed even noncontroversial provisions under a cloud in a broad challenge that seems certain to be resolved only by the Supreme Court.

It's not immediately clear what practical impact Parnell's announcement would have on Alaskans, an estimated 14 percent of which are uninsured year-round. A major expansion of the federal law is still pending, and a legal expert and health care consumer advocate say any refusal by the states to participate in the law is an invitation to the federal government to step in and implement it for them.