Charles Krauthammer said Monday on "Special Report with Bret Baier" that since President Obama is frequently changing the rules of ObamaCare on a whim, the law "exists in his head."

"You look at the stack of the papers and all the bills and all the legislation and the regulation, but in fact nobody has any idea what the law is," Krauthammer, a syndicated columnist and Fox News contributor, said. "It changes at the whim of the president every Wednesday morning. So there really is no bill. It exists in his head."

Krauthammer' comments come as the Department of Health and Human Services announced five million Americans had signed up for health coverage under the law, with only two weeks of open enrollment remaining before the March 31 deadline.

Krauthammer said additionally, ObamaCare is failing on its original goal of insuring the uninsured. He cited some estimates that only one in ten people who have enrolled in a plan were previously uninsured.

"So the original goal of this was to insure the uninsured. It's not doing that," he said. "It's disrupting all the other people who had it."