A furious Sen. Mike Lee (R-Utah) emerged from Wednesday's classified briefing by the Trump administration on the killing of Iranian Gen. Qasem Soleimani, calling it "insulting and demeaning" that briefers instructed senators not to debate the appropriateness of further military action against Iran.

"They're appearing before a co-equal branch of government responsible for their funding, for their confirmation, for any approval of any military action they might undertake. They had to leave after 75 minutes, while they were in the process of telling us that we need to be good little boys and girls and run along and not debate this in public. I find that absolutely insane. I think it's unacceptable."

— Mike Lee

Why it matters: Lee said that he entered the briefing "undecided" on whether to vote for a Senate resolution curbing President Trump's military action toward Iran and left the briefing "decided."

It's rare to see a Republican senator so harshly rebuke the Trump administration, but Lee — along with fellow libertarian-leaning Sen. Rand Paul (R-Ky.) — did not hold back on condemning officials for suggesting that members of Congress debating military action would further embolden Iran.

"They were asked repeatedly, what, if anything, would trigger the need for the administration to come back to Congress for a declaration of war or an Authorization for the Use of Military Force," Lee added. "At one point, I believe one of the briefers said something like, “I’m sure we can think of something.” But they struggled to identify anything."

Go deeper: House to vote to curtail Trump's war powers against Iran