While much of the debate over the $700 billion federal bailout plan has focused on whether the money is being spent wisely or well, concerns are growing among many conservatives about its constitutionality.

Some conservatives have argued that the law creating the program, the Emergency Economic Stabilization Act of 2008, which Congress passed hastily in October, violates constitutional principles that limit the amount of power that lawmakers can delegate to the executive branch.

They also maintain that the enormous bailout plan has illegally grown beyond its original focus on the financial services industry to include a bailout of the auto industry and more.

Robert A. Levy, the chairman of the Cato Institute, a libertarian organization in Washington, said in an interview that the bailout program, which goes by the acronym TARP for Troubled Assets Relief Program, goes beyond the realm of delegation the courts should allow. Mr. Levy said that earlier cases had found such delegation was appropriate if Congress laid down “an intelligible principle” that provided clear guidance to an agency or a regulator. But that, he said, is precisely what is missing in the bailout.