President Trump recently announced that the United States was quitting the United Nations Economic, Social, and Cultural Organization (UNESCO) for the third time. This is good news – UNESCO has championed gender ideology in education, discriminatory DEI policies, and the entire litany of woke doctrines. It has also worked to erase Jewish history in the Holy Land.

But the administration did not need to bother with formally withdrawing from the treaty — from a constitutional perspective, the U.S. hasn’t been a member at least since Trump first quit it in 2017.

When Biden sought to rejoin the Paris-based agency in 2023, he neglected to seek authorization from Congress. No one made a big deal of it then, but it means that, for domestic law purposes, the U.S. never actually rejoined.

This is an important point with implications for numerous international organizations, especially as the administration sets out on an agenda of U.N. reform. Membership in international organizations was not supposed to be a political revolving door. Congress authorizes membership at the outset. After the U.S. leaves, a whole new congressional authorization must be obtained by any president wishing to rejoin.

Under the Constitution, the president can only bring the country into a treaty with the “consent” of two-thirds of the Senate. That is a substantial hurdle, and deliberately so: Commitments to foreign countries can be harder to pull out of than domestic ones. They can become a way of imposing obligations on the country that are then out of reach of the democratic process. In the 20th century, presidents have often relied on the approval of a majority of both Houses instead, a dubious practice but now widely followed.

When the U.S. first joined UNESCO in 1946 (and the World Health Organization in 1948), President Truman was acting pursuant a law passed by both Houses authorizing him to do so.

But Congress did not reauthorize Biden’s reentry to UNESCO. Instead, he treated the 1946 authorization as a lifetime membership, when in fact it was only a one-time pass. If the U.S. quit a treaty that the Senate had ratified — say the NATO treaty — then a decision to rejoin would be subject to a new requirement of advice and consent. Congressional authorization is a stand-in for Senate ratification and should be subject to the same rules.

Consider a parallel case: If a president fires a senate-confirmed appointee, and he or a subsequent president wishes to return him to the same post, no one would argue that he could do so simply on the grounds that the Senate had previously confirmed him. Indeed, Andrew Jackson’s Attorney General resigned from his position, and was then reappointed to it — only to be rejected by the Senate.

As a statutory matter, the 1946 agreement on UNESCO allowed the president to “accept membership” — not accept, and accept, and accept again. If a congressional authorization is good for infinite rounds of quitting and rejoining, it makes getting out of international agreements harder than getting in – exactly the opposite of what the Framers intended.

The argument of perpetual authorization was invented by Jimmy Carter, who purported to rejoin the International Labor Organization in 1980 based on a 1934 authorization. President Bush neglected to seek congressional approval when he rejoined UNESCO in 2002, nearly two decades after Reagan quit. Neither instance attracted much attention, and two modern actions do not prove a constitutional rule.

There is a good argument for the Trump administration having withdrawn from UNESCO as if it were a member — to avoid any doubt or subsequent quibbling. But the administration should clarify that it is “quitting” only out of an excess of caution, and does not see the U.S. as properly joined, which is consistent with its nonpayment of any dues.

To avoid abuse by future administrations, Congress should repeal the antiquated authorizations for UNESCO and WHO, which Trump also announced withdrawal from. If a subsequent president wants to rejoin, he should have to sell it to Congress on the organization’s existing records, not the hopes and dreams of the 1940s.

Eugene Kontorovich, a professor at George Mason University Scalia School of Law, is a senior research fellow at the Heritage Foundation.