Congressional Republicans are in talks about whether they will have to vote to block President Trump’s expected new tariffs on Mexico, discussions that could set off the second impasse this year on Trump’s use of executive power to bypass Congress, The Washington Post reports. The vote—in what would be a rare act of defiance from the GOP—could also potentially block the billions of dollars Trump had said in February would be allocated to funding the border wall when he declared a national emergency at the southern border. The president’s planned tariffs on Mexico, a country with which the U.S. currently has a free-trade agreement, depends on Trump’s determination of a national emergency at the border. The law allows Congress pass a resolution of disapproval to override such a determination. In March, Congress passed this type of resolution after the president redistributed border wall funds, which he vetoed.