“It would be like saying the Canadians are having travel difficulties and the U.S. says we’ll make you U.S. passports and you can go over,” Ms. Waterman said.

Image Delby Powless of the Iroquois team, the Nationals, at the practice. Credit... Ramin Talaie for The New York Times

Only a few Indian nations issue their own passports, said Robert J. Miller, a professor at Lewis & Clark Law School in Portland, Ore., who has written extensively about federal Indian law. He said that he had never heard of the United States government objecting to the use of such a document.

Neither has Robert Anderson, who was associate solicitor for Indian affairs in the Interior Department during the Clinton administration and now directs the Native American Law Center at the University of Washington School of Law.

“The tribes will probably say, ‘Hey, we’ve got the authority to do this,’ ” he said.

But the State Department said Monday that federal law does not allow a tribal document to be used in lieu of a United States passport when traveling outside the United States. A spokeswoman said that an October 2008 internal directive emphasized that policy, though it noted that other countries had sometimes recognized such documents.

Gov. Bill Richardson of New Mexico wrote to Secretary of State Hillary Clinton and Secretary of Homeland Security Janet Napolitano on Monday to express his dismay that the players were being prohibited from traveling with their tribal passports.

“It’s a matter of tribal sovereignty and respecting the rights of the Native American population of this country,” he said in a telephone interview.

Representative Dan Maffei, a Democrat from upstate New York, said that the federal government’s refusal to recognize the Iroquois passports had the potential to be an “embarrassing situation” for the United States.