Final answer:
The Fourth Amendment, requiring officials to obtain a warrant before electronic surveillance, was applied when NSA wiretaps were challenged, particularly after the USA PATRIOT Act expanded government powers, raising concerns about privacy rights.
Step-by-step explanation:
The amendment that was applied when NSA wiretaps were called into question is the Fourth Amendment, which protects citizens against unreasonable searches and seizures. In cases such as United States v. United States District Court (1972) and Carpenter v. United States (2018), the requirement for government officials to obtain a warrant before conducting electronic surveillance was affirmed. The controversy was intensified by the implementation of the USA PATRIOT Act after the 9/11 attacks, which expanded the federal government's surveillance powers.
Nevertheless, the act's constitutionality, especially in relation to warrantless wiretaps by the NSA, has been subject to judicial scrutiny and public debate over the balance between national security and individual privacy rights.