If President-elect Donald Trump is as much a man of his word as he says he is, he’ll move the US embassy in Israel to Jerusalem shortly after he takes office. There are good diplomatic and constitutional reasons for him to do so.Congress passed the Jerusalem Embassy Act in 1995, which firmly asserted that “Jerusalem should be recognized as the capital of the State of Israel” and that our embassy should be established there “no later than May 31, 1999.” (The vote was 93-5 in the Senate and 374-37 in the House.) But the law was never implemented – because presidents Clinton, Bush and Obama all came to view it as a congressional infringement on the executive branch’s constitutional authority over foreign policy, and consistently exercised a built-in presidential-waiver clause based on their perception of national security interests.These waivers, which must be and have been signed every six months, have always been defended in terms of protecting the bedrock constitutional principal separating the executive and legislative powers. Despite the fact that two of the past three presidents (Clinton and Bush) had vowed during their campaigns to move the embassy – Clinton said he’d “always wanted to” and Bush promised to start the process on his first day in office – both later reneged. Their so-called Middle East experts had convinced them that doing so would prejudge negotiations for a final settlement between Israelis and Palestinians.All three missed the forest of Middle East reality for the trees of diplomatic denial and intransigence.The Founding Fathers were heavily influenced by French philosopher Charles Secondat, Baron de Montesquieu, most notably in connection with the separation of powers. In his The Spirit of Laws (1748), Montesquieu warned that “Were the executive power not to have a right of restraining the encroachments of the legislative body, the latter would become despotic; for as it might arrogate to itself what authority it pleased, it would soon destroy all the other powers.”James Madison was an ardent though rational advocate for such separation. In one of the Federalist Papers he wrote that “An elective despotism was not the government we fought for; but one in which the powers of government should be so divided and balanced among the several bodies of magistracy as that no one could transcend their legal limits without being effectually checked and restrained by the others.” A key but often-ignored operative word there was “balanced.”John Adams, in his Thoughts on Government, opined that “A representative assembly, although extremely well qualified, and absolutely necessary, as a branch of the legislative, is unfit to exercise the executive power, for want of two essential properties, secrecy and dispatch.” In the openly and everlastingly analyzed Palestinian-Israeli dispute, there has seldom if ever been such “secrecy and dispatch.”The Jerusalem Embassy Act noted that every country in the world has had the right to designate the capital of its choice, with Israel the lone exception. It noted that “Jerusalem is the seat of Israel’s President, Parliament, and Supreme Court, and most of its ministries and cultural institutions.”It recognized since the reunification of the city in 1967, religious freedom has been guaranteed to all.Yet since the celebration of the 3,000th anniversary of King David’s declaration of Jerusalem, in 1996, as the capital of the Jews, there’s been no progress in the physical relocation of the US Embassy.The root of the State Department’s long-standing heavy-handed reluctance to offend Arab populations in the region is a willful ignorance of history and reality. In 1948, president Harry Truman ignored its strong objections and enabled the US to become one of the first countries to recognize Israel.Even though Israel won all of Jerusalem in the 1967 war, even though no Israeli government nor popular referendum would ever allow another city to be designated its capital, even though the Arab-Palestinian peace process countenances no other place for that purpose – in the view of the State Department, Jerusalem remains no-man’s land.The issue remains so delicate that the Obama administration went to the Supreme Court to block a law passed by Congress that would allow American parents of children born in Jerusalem to list Israel as their birthplace on their passports. When Obama traveled to Jerusalem in September for the funeral of president Shimon Peres, the White House initially released a transcript of his eulogy as having taken place in “Jerusalem, Israel” – and a few hours later “corrected” it by crossing out the word “Israel.”The US government is not alone in this delusional semantic preoccupation. The Cable News Network once decided that Jerusalem was no longer in Israel and summarily removed it from the list of cities noted in CNN’s regional daily weather forecasts.Many geography books leave Israel off the world map, some still insisting that the speck of land surrounded by Arab countries be called “Palestine.”Such political and bureaucratic bone-headedness flies in the face of modern realities. It’s a wonder that US passports for people born in Israel’s holy city don’t list them as having entered the world in “Occupied Jerusalem.”There has long been bipartisan support for the Jerusalem Embassy Act. “Non-fulfillment of the law does no good to the US-Israeli relationship or to prospects for Arab-Israel peace,” said senators from both aisles to Clinton.Elliott Abrams, a former Middle East adviser to Bush, said recently that Trump should follow through on his promise because, even if east Jerusalem were eventually ceded to the Palestinians as the capital of their own state, no conceivable settlement would deny west Jerusalem to Israel. “There is simply no reason not to put a US Embassy there.”Meanwhile, the presidential veto of the Act has been ritually repeated every six months for the past 22 years. The results have been spectacularly unsuccessful.The separation of powers envisioned by the Founding Fathers was a wise principle. But it was not intended to strangle the legislative branch, or the will of the people. In this case constitutional democracy (read, an unequivocal act of Congress) should trump executive diplomacy. The pun was unintentional, but it works.The writer, a law professor at the University of Baltimore, is author of Defending Truth: The Quest for Honesty about Jews and Israel, due out in January.