RUTHFULLY YOURS

The embassy’s exact location within Jerusalem has gotten much less attention, but it is equally consequential. It will be housed in buildings used by the American Consulate, as well as in an adjacent former hotel purchased by the State Department in 2014. Most of that complex is located on the far side of the armistice line that divided Jerusalem from 1949 to 1967. Thus the embassy site demonstrates that the U.S. not only sees Jerusalem as Israel’s capital, but also—consistent with bipartisan calls from Congress—recognizes the city as unified.

The “Green Line” was created in the wake of Israel’s 1948-49 War of Independence. Upon the country’s founding, Jordan and its allies invaded, with the goal of preventing the creation of a Jewish state. Although they failed at that goal, the Arab armies did occupy significant territory when the armistice was called, including what is now widely referred to as the West Bank and East Jerusalem. Jordan subsequently expelled all Jews from the areas under its control.

In 1967, during the Six Day War, Israel recaptured these places. But in the war’s aftermath the United Nations invested the temporary 1949 armistice line with talismanic significance. The U.N. claimed Israel was “occupying” the territory that Jordan had forcibly seized not two decades earlier. Thus the international community came up with a unique demand: Israel had to keep the areas under its control, including East Jerusalem and the Old City, free of Jewish inhabitants. Any move to unify Jerusalem would be considered a war crime.

In international law, armistice lines are not borders; they merely mark breaks in the fighting. The claim that the Green Line created a permanent “Judenrein” zone in the area occupied by Jordan, or that it in any way changed the legal status of the territory on the far side, is unique and illiberal.

By ignoring the armistice line today, the U.S. is showing that it attaches no legal significance to this outdated demarcation. Having an embassy that straddles the Green Line means recognizing as Israel’s capital a unified Jerusalem that includes the Old City and other eastern areas. It means categorically rejecting the notion that Israel has no sovereign claims across the Green Line.

President Trump made this explicit last week, announcing his delegation to attend the embassy opening “in Jerusalem, Israel.” In another sign of change, the State Department’s annual human-rights report on Israel, released last month, for the first time dropped the word “occupied” from its discussion of East Jerusalem and the West Bank.

Skeptics, including the foreign-policy experts who blanched when the president announced the embassy move, are trying to construe his actions as narrowly as possible. They often cite a sentence from his December speech: “We are not taking a position on any final status issues, including the specific boundaries of the Israeli sovereignty in Jerusalem or the resolution of contested borders.” Their interpretation is that Mr. Trump did not say Jerusalem consists of any specific physical area, and certainly not anything across the Green Line.

But that sentence does not mean what they claim. The president was leaving open “final status” borders—those that might be negotiated in the future. Mr. Trump was saying that American recognition of today’s Jerusalem, with its well-known municipal boundaries, in no way would prevent Israel and the Palestinians from later agreeing on different lines.

Most proposed peace plans contemplate Israel ceding parts of its undisputed sovereign territory to a future Palestinian state. In that sense, all of Israel’s “specific boundaries,” far beyond Jerusalem, are subject to change by a final status agreement. That possibility, however, does not negate American recognition of Israel’s current borders.

Others who wish to obfuscate the significance of the new embassy’s location note that it sits in a pocket of land that was a U.N.-administered demilitarized zone from 1949-67. But the legal theory that paints Israel as an “occupier” is not based on who controlled the land during that period. Rather, the argument is that Israel does not have the right to any territory on the Green Line’s far side. The former DMZ is exactly such a location. In 1958 a U.N. Security Council resolution explicitly declared that the DMZ was “beyond” the 1949 armistice line.

All this can mean only one thing: The U.S. no longer buys into the legal theory behind claims of Israeli “occupation.” Other countries may soon follow, just as they are now announcing their intention to recognize Jerusalem. America’s affirmation of a unified city may be only the first fissure in the ossified international consensus.

Mr. Kontorovich is a director at the Kohelet Policy Forum, a Jerusalem think tank, and a professor at Northwestern University’s Pritzker School of Law School.