The stage was set for the 1937-38 collapse with the passage of the National Labor Relations Act in 1935 — better known as the "Wagner Act" and organized labor's "Magna Carta." To quote Sennholz again:
This law revolutionized American labor relations. It took labor disputes out of the courts of law and brought them under a newly created Federal agency, the National Labor Relations Board, which became prosecutor, judge, and jury, all in one. Labor union sympathizers on the Board further perverted this law, which already afforded legal immunities and privileges to labor unions. The U.S. thereby abandoned a great achievement of Western civilization, equality under the law.
The Wagner Act, or National Labor Relations Act, was passed in reaction to the Supreme Court's voidance of NRA and its labor codes. It aimed at crushing all employer resistance to labor unions. Anything an employer might do in self-defense became an "unfair labor practice" punishable by the Board. The law not only obliged employers to deal and bargain with the unions designated as the employees' representative; later Board decisions also made it unlawful to resist the demands of labor union leaders.
Armed with these sweeping new powers, labor unions went on a militant organizing frenzy. Threats, boycotts, strikes, seizures of plants and widespread violence pushed productivity down sharply and unemployment up dramatically. Membership in the nation's labor unions soared: By 1941, there were two and a half times as many Americans in unions as had been the case in 1935. Historian William E. Leuchtenburg, himself no friend of free enterprise, observed, "Property-minded citizens were scared by the seizure of factories, incensed when strikers interfered with the mails, vexed by the intimidation of nonunionists, and alarmed by flying squadrons of workers who marched, or threatened to march, from city to city."