Είναι ένας όρος που χρησιμοποιείται αποκλειστικά και μόνο στις ΗΠΑ, και κατοχυρωνεται από το Σύνταγμα. Σημαίνει ότι οποιαδήποτε απόφαση οποιουδήποτε δικαστηρίου σε μία πολιτεία θα γίνεται σεβαστή και θα εφαρμόζεται σε όλες τις υπόλοιπες πολιτείες.

In drafting the Full Faith and Credit Clause, the Framers of the Constitution were motivated by a desire to unify their new country while preserving the autonomy of the states. To that end, they sought to guarantee that judgments rendered by the courts of one state would not be ignored by the courts of other states. The Supreme Court reiterated the Framers' intent when it held that the Full Faith and Credit Clause precluded any further litigation of a question previously decided by an Illinois court in Milwaukee County v. M. E. White Co., 296 U.S. 268, 56 S. Ct. 229, 80 L. Ed. 220 (1935). The Court held that by including the clause in the Constitution, the Framers intended to make the states "integral parts of a single nation throughout which a remedy upon a just obligation might be demanded as of right, irrespective of the state of its origin."

The Full Faith and Credit Clause is invoked primarily to enforce judgments. When a valid judgment is rendered by a court that has jurisdiction over the parties, and the parties receive proper notice of the action and a reasonable opportunity to be heard, the Full Faith and Credit Clause requires that the judgment receive the same effect in other states as in the state where it is entered. A party who obtains a judgment in one state may petition the court in another state to enforce the judgment. When this is done, the parties do not relitigate the issues, and the court in the second state is obliged to fully recognize and honor the judgment of the first court in determining the enforceability of the judgment and the procedure for its execution.
http://www.answers.com/topic/full-faith-and-credit-clause

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Note added at 11 hrs (2007-01-05 08:07:28 GMT)
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Ουσιαστικά, εννοεί ότι όλες οι επίσημες αποφάσεις (πράξεις) του είναι σεβαστές και εφαρμοστέες σε οποιαδήποτε πολιτεία των ΗΠΑ.