John Conyers knows a good deal more than Donald Trump does about the Korea Peninsula—and a lot more about the Constitution.

So it is worth noting that Conyers has taken a lead in organizing congressional opposition to Trump’s bombastic threats about unleashing “fire and fury” on North Korea. He has precisely what our “locked and loaded” president lacks: the wisdom that extends from experience.

As a young volunteer with the Michigan National Guard, Conyers was called up to serve with the 1279th Combat Engineers in the Korean War. He was in the war zone for a year as a lieutenant supervising repairs and replacements of Army aircraft.

When Conyers got home, he went to law school and then, with the encouragement of the Rev. Martin Luther King Jr., began a political career that would eventually see him chair the House Judiciary Committee. His decades of experience with congressional oversight of successive presidents during the undeclared wars of the 1960s and ’70s in Southeast Asia, during Ronald Reagan’s illegal interventions in Central America in the 1980s, and during the Bush-Cheney wars in the Persian Gulf have made him an expert on questions about when and how presidents may steer the country into conflict.

Based on his experience, Conyers argues that Trump is getting everything wrong when he answers North Korean saber rattling with American saber rattling.

“As a veteran of the Korean War, I am ashamed that our Commander-in-Chief is conducting himself in a reckless manner that endangers our troops stationed in Korea and our regional allies,” explains the Michigan Democrat. “Trump must immediately cease talk of pre-emptive war—which must be authorized by Congress—and commit to the diplomatic path advocated by both American experts and the South Korean government.”

Conyers is right. And his position has attracted considerable support in Congress. For instance, while Trump claims to be concerned about threats to Guam, the congressional representative from Guam, Madeleine Bordallo, says she agrees with Conyers.

“President Trump’s statements were unhelpful, dangerous and raised tensions with North Korea higher than we have previously seen,” says Representative Bordallo. “This has led to North Korea directly threatening nearly 168,000 American citizens living in my home district of Guam. While I have great confidence in our military’s capabilities in the Pacific.… President Trump must show steady leadership to prevent further escalating tensions. I join Representative Conyers and my Democratic colleagues in calling on the Trump Administration to work with the international community and engage in diplomatic discussions with North Korea. It is imperative that President Trump and his Administration work towards a peaceful solution to this situation and refrain from any action that could lead toward a military conflict.”

Bordallo joined Conyers and 60 other House members in signing an urgent letter to Secretary of State Rex Tillerson, in which they expressed “profound concern over the statements made by President Trump that dramatically increased tensions with North Korea and raised the specter of nuclear war.”

“These statements are irresponsible and dangerous, and also senselessly provide a boon to domestic North Korean propaganda which has long sought to portray the United States as a threat to their people,” the House members declared in the August 10 letter. “Accordingly, we respectfully but firmly urge you to do everything in your power to ensure that President Trump and other Administration officials understand the importance of speaking and acting with the utmost caution and restraint on this delicate issue. Congress and the American public will hold President Trump responsible if a careless or ill-advised miscalculation results in conflict that endangers our service members and regional allies. To allay these concerns, the Trump Administration should publicly declare its agreement with the constitutional requirement that any preemptive attack on North Korea must be debated and authorized by Congress.”

That final line gets to the heart of the matter.

Trump lacks the authority to order a preemptive strike on North Korea. While the president has a responsibility to defend the United States when another country attacks, the power to declare war (and, in so doing, to authorize the use of force) rests with Congress.

John Conyers and the other members of the House who have written Trump are obeying the oaths they swore “to support and defend the Constitution of the United States against all enemies, foreign and domestic.”

Donald Trump swore a parallel oath to “preserve, protect and defend the Constitution of the United States.” Congress should remind him of that by outlining clear limits on the use of force—especially with regard to to preemptive and unilateral nuclear strikes. If House Speaker Paul Ryan chooses to try to block action, the threat that his sycophantic relationship with the president should be recognized and addressed by the chamber.

If, in the end, Trump chooses to disregard his oath, then he should be impeached and removed from office.

Should it come to that, John Conyers will, again, be able to call on wisdom grounded in experience. He is, after all, the last remaining member of the House Judiciary Committee that voted for Articles of Impeachment against Richard Nixon in July 1974.