With the stroke of a pen, a new bill in Congress could slash the number of Palestinian refugees -- and open a world of controversy.

A war is brewing on Capitol Hill. And while wars tend to create refugees, this one may result in fewer of them.

Sen. Mark Kirk (R-IL) is trying to get a handle on the real number of Palestinian refugees in the Middle East -- a move that could result in a change of status for millions of Palestinians. His proposed language for the 2013 foreign appropriations bill would require the U.S. government to confirm just how many Palestinians currently served by the U.N. Relief and Works Agency (UNRWA) -- the body taskedwith providing assistance, protection, and advocacy for Palestinian refugees -- are actually refugees. The bill, slated for markup on May 22, would challenge the status of the children, grandchildren, and great-grandchildren of Palestinian refugees -- a great many of whom claim to be refugees despite the fact that they were never personally displaced in the 1948 and 1967 Arab-Israeli wars.

The aim of this proposed legislation, Kirk's office explains, is not to deprive Palestinians who live in poverty of essential services, but to tackle one of the thorniest issues of the Palestinian-Israeli conflict: the "right of return." The dominant Palestinian narrative is that all of the refugees of the Israeli-Palestinian wars have a right to go back, and that this right is not negotiable. But here's the rub: By UNRWA's own count, the number of Palestinians who describe themselves as refugees has skyrocketed from 750,000 in 1950 to 5 million today. As a result, the refugee issue has been an immovable obstacle in round after round of negotiations between the Israelis and Palestinians.

How have these numbers swelled, particularly as the Palestinians who fled or were forced from their homes in 1948 and 1967 grew old and died? This question lies at the crux of the Kirk amendment. And the answer is UNRWA.

The knock on UNRWA is that it exists to perpetuate the refugee problem, not solve it. It was UNRWA that bestowed refugee status upon "descendants of refugees," regardless of how much time had elapsed. As a result, the Palestinian refugee population has grown seven-fold since the start of the Arab-Israeli conflict. As one study projects, if descendants maintain their current status, the number of "refugees" in 2020 will be 6.4 million -- despite the fact that few of the actual, displaced Palestinians will still be alive. In 2050, that number will reach 14.7 million.

UNRWA, which calls for a "just and durable" solution to the refugee problem, has unquestionably been a silent partner to the Palestinian leadership. The agency's administration fully understands that if Israel accepted the PLO's demand, it would be demographic suicide. As Palestinian Authority President Mahmoud Abbas himself has admitted, asking the Jewish state to repatriate 5 million Palestinians "would mean the end of Israel."

UNRWA's warts notwithstanding, American taxpayers have rewarded it year after year. In the 2011 fiscal year, U.S. assistance to UNRWA stood at $249.4 million. Total contributions since its founding in 1949 amount to a staggering $4.4 billion.

In recent years, politicians and policy wonks, including one former UNRWA administrator, have called for UNRWA reform. The agency hasn't merely demurred; it has girded for battle. UNRWAset up shop in Washington with two Hill-savvy professionals, despite the fact that its operations are entirely based in the Middle East, anticipating the need for what looks a full-scale lobby effort to defend its mission. The agency even toyed with changing its name last year in an attempt to burnish its image in the West.