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acts and laws (federal, state, or foreign)

A bill passed by Congress becomes an act or law. Capitalize when the official title is given, when using a title by which an act or a law is most commonly known, or when numbered.

But lowercase act or law when it stands alone or in shortened titles or general descriptions.
Atomic Energy Act or McMahon Act, the act
Smoot-Hawley Tariff Act; the tariff act; the act
Federal Housing Act of 1961; the housing act of 1961; the 1961 act
Immigration Reform and Control Act (IRCA)
Sherman Antitrust Act; the antitrust act; the act
Social Security Act
Walsh-Healey Act
Act of Toleration
act of Congress, the act
Public Act 26; Public Law 9
Multiple Dwelling Law, the law