U.S. President Donald Trump's declaration Dec. 6 was not U.S. policy news. In 1995, Congress passed the Jerusalem Embassy Act. The bill, aimed at providing "for the relocation of the United States Embassy in Israel to Jerusalem" declared that the city had "[s]ince 1950 ... been the capital of the State of Israel." But no American president had ever recognized Jerusalem as Israel's capital out loud -- in spite of or perhaps because of his regard for Israel's security. For that reason, the Jerusalem Embassy Act includes a presidential waiver to suspend the embassy's relocation "for a period of six months if [the president] determines and reports to Congress ... that such suspension is necessary to protect the national security interests of the United States." Each president since October 1998 has faithfully invoked the waiver every six months, continually postponing the move. Even Trump signed the document mere moments after...