Allergan and the St. Regis Mohawk Tribe have asked the Supreme Court to reverse a federal appeals court’s decision to bar a controversial tactic from being used as patent protection against inter partes reviews (IPRs).

In 2017, Allergan officially transferred the patents for its blockbuster eye drug, Restasis (cyclosporine), to the New York-based St. Regis Mohawk tribe in hopes of using the tribe’s sovereign immunity against patent challenges from drug companies like Mylan and Teva. The pair agreed to a deal that gave St. Regis $13.75 million in addition to potential annual royalties of up to $15 million.

But in February 2018, the Patent Trial and Appeal Board (PTAB) ruled that Native American tribes cannot use sovereign immunity as a defense against IPRs, and last July, a federal appeals court upheld the ruling.