“It appears from the letter that the Senators do not understand our constitutional system or the power to make binding agreements.”

– Jack Goldsmith, “The Error in the Senators’ Letter to the Leaders of Iran,” lawfareblog.com, March 9

In the continuing “dialogue” (quotations to be read sarcastically) between branches of the federal government about Iran, politics dominate, but law and decorum matter a great, great deal. The recent letter from 47 Republican senators to Iranian leaders shows why.

When freshman Sen. Tom Cotton, R-Ark., penned the letter, purporting to school Iranian leaders on the niceties of American constitutional law, he made key mistakes.

One, ironically, was the legal error described in the quote from Jack Goldsmith above. Goldsmith is no partisan opponent of the Republicans – he served in high-level legal and defense capacities in the administration of President George W. Bush. In addition, he’s a highly distinguished professor at Harvard Law School, a member of the Hoover Institute Task Force on National Security and Law, and an expert in many areas, including presidential power.

So when Goldsmith took Republican senators to task this week for getting our own Constitution wrong in their letter purporting to explain our own Constitution to officials in Iran, it was with a voice carrying gravitas of the highest order.

As Goldsmith pointed out, the letter to Iran indicates that the U.S. Senate ratifies treaties. It doesn’t. The Senate provides its advice and consent once it is presented a treaty by the president; if the Senate then provides its approval by a two-thirds vote, it is up to the president to then ratify the treaty, which at that point is in his discretion.

Of course, the current effort by the opposition isn’t even addressing a treaty, but rather, the executive action that the administration of President Barack Obama would utilize to formalize any agreement between Iran and the P5+1 nations, which include the United States.

The letter lets Iran know that any executive order made by one president can be undermined by the next. And while getting the law about treaties wrong, this statement was in all likelihood true.

True or not, however, the letter missed the point in at least two ways that are damaging to the U.S. in its dealings with nations across the world.

First, it intends to undercut the negotiating posture of the executive branch. Because these members of Congress don’t agree with what they believe to be the terms of an incipient agreement, they are voicing their opinion directly to Iran. Their goal seems to be to scuttle an agreement or gain political favor, or perhaps both.

Vice President Joe Biden said he had never witnessed such an act by senators in his many decades in that robust institution. This type of intrusion makes negotiations difficult, if not impossible, as the executive branch is prevented or severely curtailed from doing its job.

Some have asserted that the conduct of the 47 rises to the level of treason or violation of the Logan Act, by which American citizens are precluded from direct intervention in foreign policy with other nations. It is doubtful the letter presents that kind of illegality. But the policy impact is dramatic and notably unhelpful in how America conducts its foreign policy.

The second way in which the letter damages U.S. policymaking is that the action of Cotton and his colleagues represents unquestionably bad judgment in the context of the Iran issue. Why? Because there is almost no predicting which way their letter will affect either the prospective agreement or its aftermath.

Iran has reacted with characteristic venom to the letter. So if the goal of the signers was to scuttle a deal, their action, if anything, is likely to have no effect or even a positive impact on the agreement going forward.

And if the senators seek political advantage, the letter could boomerang in the worst way. As Daniel Drezner wrote this week in the Washington Post, “If – still a big if – Obama successfully negotiates a deal in the spring, that deal will have until January 2017 to marinate before the next president has the opportunity to scuttle the executive agreement. If Iran acts in a dodgy fashion, that’s one thing. If, however, they honor the terms as well as they’ve honored the interim deal, then the next president will be trying to sabotage an agreement that tamped down a major stressor in the region.”

So the letter writers got the law partly wrong, they jeopardized how America conducts foreign policy, and their political calculations might spin out of control.

With six of 10 Americans consistently supporting some form of agreement to curb Iran’s nuclear ambitions, this transparent gambit hardly seems worth the risks.