Which provision of the U.S. Constitution allows a plaintiff to enforce a judgment in an adjacent state without filing a new lawsuit?

The Full Faith and Credit Clause is the provision of the U.S. Constitution that ensures that judgments made in one state are recognized and enforceable in other states. This clause, found in Article IV, Section 1, mandates that each state must respect the public acts, records, and judicial proceedings of every other state. Essentially, it means that if a plaintiff successfully obtains a judgment in one state, they can enforce that judgment in a neighboring or any other state without needing to initiate a new lawsuit.

This provision is critical for maintaining consistency and cooperation among states in the American legal system. It promotes fairness and prevents the complications that could arise if states refused to recognize each other's legal proceedings. The Full Faith and Credit Clause creates a foundation for interstate legal enforcement and encourages individuals to resolve their disputes knowing that their judgments will be recognized, which ultimately enhances interstate relations and legal harmony.

The other clauses mentioned, such as the Due Process Clause and the Equal Protection Clause, address individual rights and protections under the law but do not specifically pertain to the enforcement of judgments across state lines. The Contracts Clause relates to the regulation of state laws regarding contracts but doesn't address the recognition of judicial decisions like the Full Faith and Credit Clause does.