first impression

A new legal issue or interpretation that is brought before a court.  In a case of first impression, the exact issue before the court has not been addressed by that court, or within that court's jurisdiction, thus there is no binding authority on that matter.

Cases of first impression often occur in connection with recently passed legislation, or when that issue has been addressed by other jurisdictions, but not in the jurisdiction of the presented court.

Courts may seek guidance from other jurisdictions, or by making analogies to related or similar issues.