SANTA CLARITA, Calif. -- A little girl is being taken from the only family she has known after a Native American tribe won a long and bitter custody battle -- based on a law that few know about.

Lexi's foster dad, Rusty, sobs after she is driven away CBS News

It was a tearful scene outside the Page family home in Santa Clarita, as their foster daughter -- 6-year-old Lexi -- was taken away by state authorities.

Earlier, a devastated Rusty Page acknowledged that he and his wife had lost a nearly four-year legal battle to adopt the little girl.

"With very heavy hearts we're complying with the order."

Lexi came to live with Page and his wife when she was two, and they have been trying to adopt her ever since.

But Lexi is part Native American, and the Indian Child Welfare Act works to keep Native American children with their tribal relatives.

Lexi's foster father walks her out of their home as she is taken to live with relatives in Utah CBS News

On Monday, the Pages learned Lexi will be going to live with her extended family in Utah.

"It's like getting a phone call that your kid was hit by a car. How do you cope with that phone call," Page asked.

Page's neighbors have been camped out near his home since Friday in support of the family, and hoping authorities will change their minds.

Neighbors protest the decision to take Lexi from her foster parents CBS News

Court records show Lexi's biological father has an extensive criminal record and her mother had a substance abuse problem. They lost custody of Lexi when she was 17 months old.

The Choctaw tribe agreed to let Lexi stay with the Pages until she could be re-united with relatives. The tribe's statement Monday said "the Choctaw nation desires the best for this Choctaw child."

"Whether it's a Native American kid or not, have the same end goal -- which is to reunite a child with his or her biological relatives so they can be raised into the family they were born into," a lawyer for the tribe said.

The Pages say they are the only family Lexi knows. They told CBS News they plan to take the case to the California Supreme Court.