UPDATE: A Steely Look at Steel: Commerce Directed to Prioritize Investigation of the Effects of Steel Imports on National Security [May 1, 2017] [open pdf - 134KB]
"On April 20, 2017, President Trump issued a Presidential Memorandum ('Memorandum') directing the Secretary of Commerce ('Secretary') to prioritize investigating the effects of steel imports on national security pursuant to Section 232(b) of the Trade Expansion Act of 1962. Under the Act, if the Secretary determines that steel 'is being imported into the United States in such quantities or under such circumstances as to threaten to impair the national security,' the President is authorized to take actions 'to adjust the imports of the article and its derivatives so that such imports will not threaten to impair the national security.' While not explicitly specified by the statute, such actions might include imposing import quotas, imposing license fees on imported goods, or negotiating trade agreements that otherwise restrict the importation into or exportation to the United States of the imported article."
CRS Legal Sidebar, May 1, 2017
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html