The Los Angeles Times has reported today that the country music supergroup Dixie Chicks has sued its label, Sony Music Entertainment, for over $4 million in royalties.

The group has also sued to sever the seven-album deal it signed with Sony in 1997. Their debut album, Wide Open Spaces, and its follow-up, Fly, have together sold nearly 20 million copies and have brought in over $175 million.

The trio, consisting of Natalie Maines Pasdar, Emily Robison, and Martie Seidel, allege that Sony has been involved in “systematic thievery” of the royalties due the label’s artists.

In a released press statment, the Dixie Chicks have asserted, “We refuse to sit back and silently endorse this behavior simply because this is a ‘standard’ practice at Sony. ... This is about people keeping their word.”

Sony has yet to comment, though it had previously brought suit against the Chicks for five undelivered albums in an amount surpassing $100 million. The company has officially claimed in court that this is a “sham attempt” by the group to pull out of its contract.