This is neither news nor a new topic, but I post it here to publicize the law during the current revolt against U.S. immigration laws by employers who would privatize profits and socialize costs.
Quote Originally Posted by 8 USC § 1182 - Inadmissible aliens
(A) Labor certification

(i) In general
Any alien who seeks to enter the United States for the purpose of performing skilled or unskilled labor is inadmissible, unless the Secretary of Labor has determined and certified to the Secretary of State and the Attorney General that—

  • (I) there are not sufficient workers who are able, willing, qualified (or equally qualified in the case of an alien described in clause (ii)) and available at the time of application for a visa and admission to the United States and at the place where the alien is to perform such skilled or unskilled labor, and
  • (II) the employment of such alien will not adversely affect the wages and working conditions of workers in the United States similarly employed.

(ii) Certain aliens subject to special rule
For purposes of clause (i)(I), an alien described in this clause is an alien who—

  • (i) is a member of the teaching profession, or
  • (ii) has exceptional ability in the sciences or the arts.
  • (iii) Professional athletes . . .

http://www.law.cornell.edu/uscode/text/8/1182