Arizona’s Republican Sen. Jeff Flake has made no secret of his contempt for President Donald Trump. After suggesting over the weekend that Trump should be challenged in the 2020 primaries, he went on to introduce legislation Monday to invalidate Trump’s steel and aluminum tariffs.

According to Flake: “If we enter a trade war, we risk reversing those gains we have made. We in Congress simply can’t be complicit as this administration courts economic disaster in this fashion.”

The Hill reports: Flake… made a wide-reaching pitch to his colleagues from the Senate floor, saying if they are concerned about the tariffs, support free trade or want to continue the recent economic gains then they should support his legislation.“You can be pro-growth; you can be pro-tariff, but you can’t be both. … I would urge my colleagues to join me in exercising our constitutional oversight and to invalidate these irresponsible tariffs,” he said.