The Norris–La Guardia Act (1932) declared that the members of labour unions should have “full freedom of association” undisturbed by employers. The act also barred the federal courts from issuing injunctions to prevent strikes, picketing, or boycotts by labour groups and prohibited “yellow-dog” contracts (Britannica).
The NLRA protects workplace democracy by providing employees at private-sector workplaces the fundamental right to seek better working conditions and designation of representation without fear of retaliation (NLRB National Labor Relation Board).
The Labor Management Reporting and Disclosure Act of 1959 (also "LMRDA" or the Landrum–Griffin Act) grants certain rights to union members and protects their interests by promoting democratic procedures within labor organizations. The Act establishes a Bill of Rights for union members; reporting requirements for labor organizations, union officers and employees, employers, labor-relations consultants, and surety companies; standards for the regular election of union officers; and safeguards for protecting labor organization funds and assets (UAW).
The Labor–Management Relations Act of 1947, sponsored by Sen. Robert A. Taft (Ohio) and Rep. Fred A. Hartley, Jr. (New Jersey), while preserving the rights of labour to organize and to bargain collectively, additionally guaranteed employees the right not to join unions (outlawing the closed shop); permitted union shops only where state law allowed and where a majority of workers voted for them; required unions to give 60 days’ advance notification of a strike; authorized 80-day federal injunctions when a strike threatened to imperil national health or safety; narrowed the definition of unfair labour practices; specified unfair union practices; restricted union political contributions; and required union officers to deny under oath any Communist affiliations (Britannica)