The U.S. Supreme Court appeared closely divided on Monday as it considered whether Congress overstepped its authority in passing a law designed to allow American citizens born in Jerusalem to have Israel listed as their birthplace on passports.

Congress passed the law in 2002 but the government has never enforced it. Seeking to remain neutral on the hotly contested issue of sovereignty over a city holy to Jews, Muslims and Christians, the State Department allows passports to name Jerusalem as a place of birth, with no country name included.

The parents of a Jerusalem-born 12-year-old boy, U.S. citizen Menachem Zivotofsky, have waged a long court battle to have his passport state he was born in Israel.