Washington (AFP) - After a long trek through the US legal system, a seemingly simple car crash case involving a chauffeur shuttling patrons from an Indian casino has landed in the nation's top court.

The US Supreme Court on Monday considered a case closely monitored by federal authorities that could redefine the legal sovereignty framework of US Indian tribes.

Native American tribes can control their own internal affairs and establish courts as federally recognized "domestic dependent nations," but they are also subject to treaties and federal laws passed in Washington.

The dispute up for consideration arose in 2011 when limousine driver William Clarke, employed by the Mohegan Tribal Gaming Authority, crashed into a car owned by Brian and Michelle Lewis in the eastern US state of Connecticut.

The pair sued Clarke but the defendant invoked sovereign immunity because he was working as a tribal employee at the time of the crash.

Connecticut's top judges decided in Clarke's favor: though the incident occurred in a US state, he was working for a sovereign tribe at the time.

The Supreme Court appeared on Monday to be receptive to the Lewis argument.

"Why should a tribal employee driving a limo be entitled to immunity?" Justice Samuel Alito questioned at one point.

"You say that the purpose of official immunity is to protect, quote, 'the fearless, vigorous, and effective administration of policies of government,' -- but you want to encourage limo drivers... to be fearless in the way they drive?"

The US Department of Justice has asked the Supreme Court to override Connecticut's highest state court.

The Supreme Court justices are slated to announce their decision by the end of June.