President Trump holds up a memorandum that reinstates sanctions on Iran after he announced his decision to withdraw from the 2015 nuclear deal on Tuesday. (Getty Images)

Back in 2015, there were loud calls — not least from senators — for President Barack Obama to ask the Senate to ratify the Joint Comprehensive Plan of Action (JCPOA) with Iran, calling it a “treaty.” Instead, he chose to enter into an executive agreement, which has become something of a trend: Treaties are a tiny fraction of international agreements overall. A 2007 study by political scientists Kiki Caruson and Victoria Farrar-Myers found that between 1977 and 1996 presidents negotiated nearly 4,000 executive agreements — but only 300 treaties.

Tuesday, though, many opponents of the agreement argued that Obama’s failure to seek ratification was what allowed President Trump to end it unilaterally. According to Sen. Ben Sasse (R-Neb.): “Donald Trump isn’t ripping up a treaty. … President Obama made a bad deal with Iran without support from Congress, and today President Trump is pulling out of President Obama’s personal commitment, and he doesn’t need Congress’s support to do so.” Rep. Ron DeSantis (R-Fla.) tweeted that “President Trump had every right to withdraw the U.S. from what was effectively an Obama executive agreement.”

Perhaps these lawmakers are fans of Thomas Jefferson’s 1801 manual on parliamentary practice, which reads, “Treaties being declared, equally with the laws of the United States, to be the supreme law of the land, it is understood that an act of the legislature alone can declare them infringed and rescinded.”

But presidents haven’t necessarily “understood” things the same way.

It’s surely possible that a treaty, in place of an executive agreement, would have wider support. Republicans would have had to vote to ratify it, and thus its abrogation might carry higher political costs. As I noted in 2015, “the difference between seeking a treaty and negotiating an executive agreement is, at base, a political question. So is the outcome of either.” And as political scientists Glen Krutz and Jeffrey Peake argue in their book “Treaty Politics and the Rise of Executive Agreements,” executive agreements conducted in “truly unilateral fashion” without even tacit congressional cooperation will be “codified but essentially hollow.”

Yet all else being equal, calling the JCPOA a “treaty” and getting Senate ratification would not have protected it from a presidential decision that it was “a horrible one-sided deal that should never, ever have been made.” In 1978, after all, President Jimmy Carter gave notice that the United States was going to withdraw from its 1954 Mutual Defense Treaty with Taiwan — thereby nullifying an agreement that had been so ratified. By doing so, Carter enabled diplomatic relations with the People’s Republic of China, completing a process begun by President Richard Nixon’s famous (and even operatic) visit to Beijing.

Similarly, in December 2001, President George W. Bush informed Russian President Vladimir Putin (yes, the same one) that the United States would withdraw from the 1972 Anti-Ballistic Missile (ABM) Treaty. This time the prompt came from internal debates: The Bush administration wanted to implement a missile defense program that the treaty prohibited.

In neither case did Congress as a whole seek to take up Jefferson’s mantle. The Senate did vote to protest Carter’s action. But in the 2002 case, when Bush abrogated the ABM Treaty, as former senator Russ Feingold tells it, that body took no action at all — and even blocked Feingold from joining a lawsuit brought against the Bush administration by more than 30 House members.

In the Taiwan case, Carter’s chief antagonist was Sen. Barry Goldwater (R-Ariz.), who argued that the president had set “a dangerous precedent for executive usurpation of Congress’s historically and constitutionally based powers.” A district court judge agreed — but the D.C. Circuit did not, holding that since a president could decide whether to move forward with a treaty even after ratification, he had “the constitutional initiative in the treaty-making process.”

The question went to the Supreme Court — which refused to comment on the merits. It effectively dismissed the case, holding that the question was a political question beyond the court’s capacity. Justice Lewis Powell’s concurring opinion noted that such a case might be justiciable someday — but at present “it cannot be said that either the Senate or the House has rejected the President’s claim. If the Congress chooses not to confront the President, it is not our task to do so.”

With no such confrontation in sight, the D.C. District Court took the same stance in 2002. The House members’ suit was set aside both because its members had no standing to sue and because they could not be said to speak for Congress. “Since President Bush announced his intention to withdraw from the ABM Treaty, neither the House nor Congress has made any attempt whatsoever to register disapproval as a body, or to insist on a role in the termination of the Treaty.”

In 1979 and 2002, legislative ire seemed to be driven more by partisanship and policy preference than by constitutional principle. In 1979, Goldwater’s suit was opposed by Sen. Ted Kennedy (D-Mass.) and supported by Sen. Orrin G. Hatch (R-Utah). But in 2001, their roles flipped. Kennedy attacked Bush’s action — and Hatch prevented a Senate resolution asserting that body’s role in treaty termination from coming to a vote.

Even Sen. Robert Byrd (D-W.Va.), vigilant advocate of Senate prerogative, noted on the Senate floor in December 2001 that Bush had the right to abrogate the ABM treaty. “I don’t question the president’s legal right to do that. That is not the question,” Byrd said.

But he did suggest that law and wisdom might diverge. “I think the president should have asked for some advice from the Senate,” the senator went on. “He does not have to take the advice, but I have seen no evidence of the president seeking advice on this matter. He simply made up his mind to do it and did it. … I think the administration would be much wiser if it took the Senate into consideration and had some expression of support. Let the American people hear some debate in the Senate.”

That’s probably good advice whether the president is rescinding a treaty, drafting an international agreement — or tearing one up.