Sen. Rand Paul (R-Kentucky) on Fox News. Fox News Sen. Rand Paul (R-Kentucky) thinks the White House is pushing increasingly ridiculous legal arguments in the fight against the Islamic State group (also known as ISIS).

In order to justify its airstrikes against the Islamic State jihadists, President Barack Obama's administration has cited authorizations for military force that date back to 2001 and 2002.

Paul, a likely presidential candidate in 2016, called that argument "absurd" four times in a Wednesday interview on Fox News. He noted the Islamic State didn't even exist in its current form at the time of the two authorizations.

"Both of those I'd say would be absurd contentions. Basically, in 2001 we voted for an authorization that said the people who attacked us on 9/11, that we would go after them. Well, this [ISIS] group wasn't in existence then, and this group isn't even allied with Al Qaeda. This group is at odds with Al Qaeda. So I think it's absurd," Paul told host Greta Van Susteren. "It's absurd to try and say a linkage to a war started 15 years ago."

Earlier in the week, Paul unveiled what he views as a solution to the White House's legal problem: a formal declaration of war in Congress. His office said he plans to introduce it in December when the Senate returns to session.

In his Fox News interview, Paul further said when he confronted Secretary of State John Kerry over the US' legal argument for its military strikes against the Islamic State, Kerry gave him another questionable justification: the inherent powers of the presidency defined by Article 2 of the Constitution.

"The president absolutely, clearly, by almost any legal standard that I can imagine, is not violating the Constitution; he's upholding it. Article 2 gives the president the power to do what he's doing," Kerry told Paul in a congressional committee hearing in September. "The president has the right, as the president under Article 2, to defend this nation."

Paul was unimpressed with Kerry's position, which he characterized as giving Obama "unlimited power to go to war."

"He said — which I think is absurd — he said, 'Well if [the 2001 authorization] doesn't do it, then the president has Article 2 authority to do whatever he wants. I disagree with that. And I think most constitutional scholars do. And I think most of the people in the American public do not think the president has unlimited power to go to war," Paul recalled on Fox.

View the Fox News segment below.