President Obama on Tuesday imposed a permanent ban on offshore oil drilling in parts of the Arctic and Atlantic, shoring up his environmental legacy just weeks before an executive-branch upending promised by President-elect Trump, who has vowed to expand domestic oil and gas extraction and relax environmental regulations. Obama’s announcement joins Canada Prime Minister Justin Trudeau, who has also committed to protecting the Arctic. In a statement the president said, “It would take decades to fully develop the production infrastructure necessary for any large-scale oil and gas leasing production in the region—at a time when we need to continue to move decisively away from fossil fuels.”