In this April 2, 2015 file photo, President Barack Obama speaks in the Rose Garden of the White House in Washington about the breakthrough in the Iranian nuclear talks. Snap back? Not so fast. The biggest enforcement provision in the preliminary nuclear agreement with Iran is turning into one of its mostly hotly contested elements. And this debate barely involves Iran. Instead, it concerns the Obama administration’s promise to quickly re-impose sanctions on Iran if it cheats on any part of the agreement to limit its nuclear program to peaceful pursuits. (AP Photo/Susan Walsh, File)