OPEC has advised its members to not mention oil prices when discussing policy in order to avoid US legal action over manipulating the market, sources close to OPEC told Reuters.

Proposed US legislation known as “NOPEC” has never been ratified, with previous US presidents refusing to make it law. However, President Donald Trump has been a vocal critic of the cartel, blaming it for high oil prices and urging it to increase output to relieve pressure on the market.

NOPEC, or the No Oil Producing and Exporting Cartels act, could open OPEC up to anti-trust lawsuits.

Refraining from discussing a preferred oil price level – a method OPEC uses to guide market expectations – was advised to the group by law firm White & Case. The lawyers also advised talking about the stability of the market in public discussions instead, and the pursuit of diplomatic lobbying to try and prevent the NOPEC bill from becoming law, two sources told Reuters.

“We solemnly believe that market stability, and not prices, is the common objective of our actions,” UAE Energy Minister Suhail al-Mazroui, who holds the rotating OPEC presidency this year, wrote in a letter sent to OPEC ministers on August 1.

“I would like to call upon OPEC member countries, as well as our participating non-OPEC colleagues, to refrain from any reference to prices in their commentary about our collective efforts or oil market condition,” he added.