President Kennedy stated in Executive Order 10925 that "discrimination because of race, creed, color, or national origin is contrary to the Constitutional principles and policies of the United States"; that "it is the plain and positive obligation of the United States Government to promote and ensure equal opportunity for all qualified persons, without regard to race, creed, color, or national origin, employed or seeking employment with the Federal Government and on government contracts"; that "it is the policy of the executive branch of the Government to encourage by positive measures equal opportunity for all qualified persons within the Government"; and that "it is in the general interest and welfare of the United States to promote its economy, security, and national defense through the most efficient and effective utilization of all available manpower". Which piece of legislation did President Kennedy use to claim that discrimination was a violation of the Constitution