In State of Texas v. City of Frisco, 2008 WL 828055 (E.D. Tex. Mar. 27, 2008), the court dismissed as "not ripe for adjudication", plaintiff's request for a declaratory judgment that the defendant's letter seeking the preservation of documents relating to potential litigation violated the Federal Rules of Civil Procedure. 

Specifically, the State asked the court to determine "[w]hether it is a violation of Rule 26(f) and 34 to require an entity to broadly preserve and retain any and all electronic documents based on a [demand] made before suit is filed."  Although the Federal Rules do not specifically address a party's preservation obligation, the court noted that Rule 37 required the parties to act in good faith with respect to the preservation and production of documents.  The court declined to intervene in the prospective case or issue an advisory opinion as to what constitutes good faith.