19 USC 1981 - General authority

(a) Proclamation of increase in, or imposition of, any duty or other import restriction; report to the Congress; adoption of resolution of approval; request for additional information 

(1) After receiving an affirmative finding of the United States International Trade Commission under section 1901 (b) of this title with respect to an industry, the President may proclaim such increase in, or imposition of, any duty or other import restriction on the article causing or threatening to cause serious injury to such industry as he determines to be necessary to prevent or remedy serious injury to such industry.
(2) If the President does not, within 60 days after the date on which he receives such affirmative finding, proclaim the increase in, or imposition of, any duty or other import restriction on such article found and reported by the United States International Trade Commission pursuant to section 1901 (e)1 of this title
(A) he shall immediately submit a report to the House of Representatives and to the Senate stating why he has not proclaimed such increase or imposition, and
(B) such increase or imposition shall take effect (as provided in paragraph (3)) upon the adoption by both Houses of the Congress (within the 60-day period following the date on which the report referred to in subparagraph (A) is submitted to the House of Representatives and the Senate), by the yeas and nays by the affirmative vote of a majority of the authorized membership of each House, of a concurrent resolution stating in effect that the Senate and House of Representatives approve the increase in, or imposition of, any duty or other import restriction on the article found and reported by the United States International Trade Commission.

For purposes of subparagraph (B), in the computation of the 60-day period there shall be excluded the days on which either House is not in session because of adjournment of more than 3 days to a day certain or an adjournment of the Congress sine die. The report referred to in subparagraph (A) shall be delivered to both Houses of the Congress on the same day and shall be delivered to the Clerk of the House of Representatives if the House of Representatives is not in session and to the Secretary of the Senate if the Senate is not in session.

(3) In any case in which the contingency set forth in paragraph (2)(B) occurs, the President shall (within 15 days after the adoption of such resolution) proclaim the increase in, or imposition of, any duty or other import restriction on the article which was found and reported by the United States International Trade Commission pursuant to section 1901 (e) of this title.
(4) The President may, within 60 days after the date on which he receives an affirmative finding of the United States International Trade Commission under section 1901 (b)1 of this title with respect to an industry, request additional information from the United States International Trade Commission. The United States International Trade Commission shall, as soon as practicable but in no event more than 120 days after the date on which it receives the Presidents request, furnish additional information with respect to such industry in a supplemental report. For purposes of paragraph (2), the date on which the President receives such supplemental report shall be treated as the date on which the President received the affirmative finding of the United States International Trade Commission with respect to such industry.
(b) Maximum rate of increase 
No proclamation pursuant to subsection (a) of this section shall be made
(1) increasing any rate of duty to a rate more than 50 percent above the rate existing on July 1, 1934, or, if the article is dutiable but no rate existed on July 1, 1934, the rate existing at the time of the proclamation.
(2) in the case of an article not subject to duty, imposing a duty in excess of 50 percent ad valorem.

For purposes of paragraph (1), the term existing on July 1, 1934 has the meaning assigned to such term by paragraph (5) of section 18861 of this title.

(c) Reduction, termination, or extension of increase in, or imposition of, any duty or other import restriction 

(1) Any increase in, or imposition of, any duty or other import restriction proclaimed pursuant to this section or section 7 of the Trade Agreements Extension Act of 1951
(A) may be reduced or terminated by the President when he determines, after taking into account the advice received from the United States International Trade Commission under subsection (d)(2) of this section and after seeking advice of the Secretary of Commerce and the Secretary of Labor, that such reduction or termination is in the national interest, and
(B) unless extended under section 2253 of this title, shall terminate not later than the close of the date which is 4 years (or, in the case of any such increase or imposition proclaimed pursuant to such section 7, 5 years) after the effective date of the initial proclamation or October 11, 1962, whichever date is the later.
(2) Repealed. Pub. L. 93–618, title VI, § 602(d), Jan. 3, 1975, 88 Stat. 2072.
(d) Review of developments with respect to industries concerned; annual report to President; advice of probable economic effect; considerations; investigations; hearings 

(1) So long as any increase in, or imposition of, any duty or other import restriction pursuant to this section or pursuant to section 7 of the Trade Agreements Extension Act of 1951 remains in effect, the United States International Trade Commission shall keep under review developments with respect to the industry concerned, and shall make annual reports to the President concerning such developments.
(2) Upon request of the President or upon its own motion, the United States International Trade Commission shall advise the President of its judgment as to the probable economic effect on the industry concerned of the reduction or termination of the increase in, or imposition of, any duty or other import restriction pursuant to this section or section 7 of the Trade Agreements Extension Act of 1951.
(3) Repealed. Pub. L. 93–618, title VI, § 602(d), Jan. 3, 1975, 88 Stat. 2072.
(4) In advising the President under this subsection as to the probable economic effect on the industry concerned, the United States International Trade Commission shall take into account all economic factors which it considers relevant, including idling of productive facilities, inability to operate at a level of reasonable profit, and unemployment or underemployment.
(5) Advice by the United States International Trade Commission under this subsection shall be given on the basis of an investigation during the course of which the United States International Trade Commission shall hold a hearing at which interested persons shall be given a reasonable opportunity to be present, to produce evidence, and to be heard.
(e) Conformity of trade agreements with this section 
The President, as soon as practicable, shall take such action as he determines to be necessary to bring trade agreements entered into under section 1351 of this title into conformity with the provisions of this section. No trade agreement shall be entered into under section 1821 (a) of this title unless such agreement permits action in conformity with the provisions of this section.
[1] See References in Text note below.