In Munro v. United States (1937), the Supreme Court ruled on a case involving the interpretation of tax laws related to stock dividends. The petitioner, Mrs. Munro, had received stock dividends from two companies and did not include them in her gross income for federal tax purposes based on an earlier court ruling that such dividends were capital assets rather than taxable income. However, after she filed her taxes, Congress amended the law to clarify that all types of stock dividends should be considered as taxable income regardless of their source or form. The IRS then sought back taxes from Mrs. Munro under this new amendment which she contested arguing it was being retroactively applied against her violating due process rights under Fifth Amendment protections against ex post facto laws and double jeopardy. However, the Supreme Court upheld lower courts' decisions favoring IRS stating that while generally legislation cannot apply retrospectively without clear intent by legislature; in this instance there was sufficient evidence showing Congress intended for amendment to apply retroactively thus making these previously untaxed dividend stocks subject to taxation.

In the dissenting opinion for Munro v. United States, Justice Cardozo disagreed with the majority's decision to uphold a conviction based on evidence obtained through wiretapping. He argued that this violated the Fourth Amendment's protection against unreasonable searches and seizures. In his view, wiretapping constituted an invasion of privacy equivalent to physical intrusion into a person’s home or office without their consent or knowledge. The use of such evidence in court proceedings was therefore unconstitutional according to him. Furthermore, he contended that allowing law enforcement agencies to engage in such practices would set a dangerous precedent and could lead to widespread abuses of power and violations of civil liberties.