The protocol requires signatories to let the International Court of Justice (ICJ) make the final decision when their citizens say they have been illegally denied the right to see a home-country diplomat when jailed abroad.

The United States initially backed the measure as a means to protect its citizens abroad. It was also the first country to invoke the protocol before the ICJ, also known as the World Court, successfully suing Iran for the taking of 52 U.S. hostages in Tehran in 1979.

But in recent years, other countries, with the support of U.S. opponents of capital punishment, successfully complained before the World Court that their citizens were sentenced to death by U.S. states without receiving access to diplomats from their home countries.