It took a while for Republicans to catch on to what President Obama is doing with the U.S. terrorist prison in Guantanamo Bay, Cuba. But now that it’s clear Obama is rushing to empty the place, Republicans are stepping up efforts to stop him. Whether they succeed could have a serious impact on national security, as well as on more general GOP efforts to rein in runaway executive power in the White House.

Obama has accelerated Guantanamo releases and transfers since last November’s midterm elections. Other than the five senior Taliban leaders released in exchange for Army Sgt. Bowe Bergdahl last May — a deal Obama made in secret, ignoring the law that required him to notify Congress — the president released just one other Guantanamo inmate in 2014 before the elections.