Answer: Taft-Hartley Act
Explanation: The Taft – Hartley Act, or originally known as The Labour Management Relations Act of 1947, is a United States law, a federal law, that limits the power, jurisdiction, and activities of unions. Adopted by Congress despite veto by President Truman, the law deals with labour and labour relations, duties and workers' rights, and one of those rights is that workers don't have to necessarily become members of a union unless they want to. This Act is considered to have eliminated the unfair practices of trade unions towards workers.