JANE COWAN: "Honour the treaties" has been a mantra in Indian country when dealing with the US government.

But now the Cherokee people of Oklahoma are asking a judge to let them expel descendants of the freed slaves once kept by their tribe in spite of a 150-year-old treaty they signed with the US government - an agreement that's been called the Indian version of the US Civil Rights Act, a document that guarantees the rights and protection of freed slaves.

JON VELIE: What we're dealing with is the ripping away of the heritage and civil and property rights of a people who're a minority. We're dealing with an oppressed group of people that's oppressing another group of people.

JANE COWAN: Jon Velie is the lead counsel representing the descendents of the slaves, known as the Cherokee Freedmen.

JON VELIE: The Cherokee Freedmen have been with the Cherokee legally for seven generations - 148 years. That is longer than most Americans can trace to an American ancestor. And in the era of Obama, the first African-American president, that feels completely wrong.

JANE COWAN: The Cherokee Nation has a population of about 300,000, including about 30,000 descendents of Cherokee Freedmen.

That the Cherokee kept slaves is one of the lesser known dimensions of a complicated chapter in American history.