A U.S. appeals court on Friday rejected a novel strategy adopted by drug company Allergan PLC to shield patents from review by an administrative court by transferring them to a Native American tribe.

The U.S. Court of Appeals for the Federal Circuit said a tribunal run by the U.S. Patent and Trademark Office has authority to review the validity of patents covering Allergan’s dry eye drug Restasis.

Allergan spokeswoman Amy Rose declined to comment.

Restasis last year generated $1.5 billion in revenue for Allergan.

In 2016 generic drug company Mylan NV , seeking to sell its own lower-cost version of Restasis, asked the Patent Trial and Appeal Board to invalidate the Allergan patents on the grounds that they described obvious ideas.