President Barack Obama surprised environmentalists and the fossil fuel industry alike when he announced a permanent, sweeping ban on oil drilling in much of the U.S. waters in the Arctic and Atlantic on Tuesday, in a decision that experts say would be difficult for a future administration to reverse.

The ban, which prevents offshore drilling from Virginia to New England and in much of the U.S. Arctic, joins an effort announced by Canada this week to prohibit oil exploration in northern Canadian waters as well. Given low prices for oil and the difficulty of deep water extraction, particularly in the frigid north, the industry hasn't exactly been chomping at the bit. But environmentalists have long warned about the future