After it was reported last week that Allergan Plc had made a deal with a Native-American tribe to stop generic drug-makers using their patents, the U.S Senator – Sherrod Brown – promised to look into how Congress can ”close loopholes that drug companies exploit to avoid competition.” Senator Brown said the “decision rips off consumers” and cannot “become the new normal”, according to Reuters.

Brown’s staff have requested a meeting with Allergan representatives to press them about the transaction. Allergan said it has reached out to Brown’s office “to provide the facts and context around this agreement with the Saint Regis Mohawk Tribe.”

Legal experts said if Allergan’s strategy is widely copied, generic drug companies will lose access to an effective venue for these patent disputes and brand-name drug companies will have an easier time preserving their monopolies on various medicines. Allergan has said the maneuver is only intended to shield the company’s Restasis patents from review at the patent board and would not affect patent challenges filed in federal court.

“We have clearly stated that this agreement with the Tribe has no impact on the pending patent litigation regarding the Restasis patent family which recently completed a five-day trial in Federal District Court in Marshall, Texas,” Allergan said in a statement.

Allergan Chief Executive Officer Brenton Saunders told Reuters on Monday the patent board is a flawed court and that Congress did not intend for it to be a major forum for pharmaceutical patent disputes.

Brown objected last year to Allergan’s proposed merger with Pfizer Inc, through which Pfizer would have slashed its tax bill by redomiciling to Ireland where Allergan is registered. Brown has also worked on legislation that would lower drug prices and increase access to cheaper “biologic” copies of certain prescription drugs.