Yellowstone Gateway Protection Act This bill withdraws specified National Forest System land in the Custer Gallatin National Forest in Park County, Montana, identified on the map titled "Emigrant Crevice Proposed Withdrawal Area," dated November 10, 2016, from (1) location, entry, and patent under mining laws; and (2) disposition under all laws pertaining to mineral and geothermal leasing. Any land within the withdrawal area that is acquired by the federal government after enactment of this bill must be immediately withdrawn in accordance with this bill.