President Trump has no authority to launch a pre-emptive strike against North Korea without congressional approval, a group of Senate Democrats argued Tuesday.

“There is no theory of Article II power that is commonly acceptable that allows for the president to launch a pre-emptive attack when the United States is not under imminent threat without congressional approval,” Sen. Chris Murphy, D-Conn., told reporters Tuesday.

That argument invokes an understanding of the Constitution that would represent a significant rollback of modern presidential power if honored. But the application of that principle to the Korean Peninsula would mark a significant shift in policy toward the North Korean regime, which is trying to develop a intercontinental ballistic missile capable of delivering a nuclear warhead to the mainland United States.

“I do not believe that the mere possession of a weapon that can hit the United States constitutes is an imminent threat,” said Murphy, a member of the Senate Foreign Relations Committee. “If that were the case, then the president would have full war making authority against any country that has an ICBM capable of hitting the United States with a nuclear warhead.”

Murphy said that several prominent Senate Democratic leaders will join him in introducing a resolution reminding Trump of that constraint. His allies include Vermont Sen. Bernie Sanders, Cory Booker of New Jersey, and Hawaii’s Brian Schatz.

That idea is at odds with long-standing U.S. policy, as past presidents and defense leaders have vowed not to allow North Korea to obtain such a weapon. “No president, Republican or Democrat, has ever forsworn the first strike capability,” Secretary of State Rex Tillerson said Monday evening during a Senate hearing. “That has served us for 70 years."

But Senate Democrats don’t trust Trump to wield that power, even though they respect his national security team. The lawmakers argued that he might overrule Tillerson and Defense Secretary Jim Mattis without serious thought.

“I don't have any trust in his willingness or ability to make sound critical decisions when it comes to North Korea,” said Sen. Tammy Duckworth, D-Wis., who joined Murphy on Tuesday’s call. “Congress must take the president saber-rattling seriously and exercise it's constitutional responsibility.”

Mattis, who appeared alongside Tillerson during Monday’s hearing, tried to reassure lawmakers that is an incorrect view.

"I think that we have to keep trust, keep faith in the system that we have that has proven effective now for decades,” he said. “I would not say it's ad hoc. It's extremely rigorous: the discussions and the step through process for decision-making.”

The prospect of a congressional debate over a prospective attack on North Korea is complicated by the possibility that the North Koreans would respond by launching their own pre-emptive strike. But Murphy maintained that the Constitution is on his side.

“There's no provision of the Constitution that waives Congress's war-making authority based on statements of foreign governments,” he said.