New York City ? The teams participating in the World Lacrosse Championships in England represent 30 nations, from Argentina to Latvia to South Korea to Iroquois.

The Iroquois helped invent lacrosse and, in a rare example of international recognition of American Indian sovereignty, they participate at every tournament as a separate nation. But they might not be at this year’s world championship tournament because of a dispute over the validity of their passports.

The 23 players have passports issued by the Iroquois Confederacy, a group of six Indian nations overseeing land that stretches from upstate New York into Ontario, Canada.

The U.S. government says it will only let players back into the country if they have U.S. passports, a team official said. The British government, meanwhile, won’t give the players visas if they cannot guarantee they’ll be allowed to go home, the official said.