The exclusionary rule of evidence applies to:

The exclusionary rule of evidence is a fundamental principle in the U.S. legal system that prohibits the use of evidence obtained in violation of a defendant's constitutional rights, particularly the Fourth Amendment, which protects against unreasonable searches and seizures. This rule is rooted in U.S. Constitutional law, making it applicable in federal courts across the United States.

Although states like Illinois may adopt similar principles or enhance protections beyond those provided by the Constitution, the foundational authority of the exclusionary rule comes from the U.S. Constitution itself. The rule was established by the U.S. Supreme Court in landmark cases such as Mapp v. Ohio, which extended the exclusionary rule to state courts, emphasizing its role in enforcing constitutional rights.

The other options reflect different aspects of law. Illinois law and common law do not fundamentally establish the exclusionary rule, although state law can incorporate it. U.S. Supreme Court law does play a role in interpreting the Constitution and applying the exclusionary rule, but it does so as an arm of the broader U.S. Constitutional law framework. Therefore, identifying the exclusionary rule as applicable under U.S. Constitutional law is accurate and reflects its primary legal foundation.