District Judge Wilson Fields did not determine if Landrieu, a Democrat, is a resident of Louisiana. He said the U.S. Constitution's requirement that senators must be residents of their states at the time of election means residency is only an issue on election day.
Landrieu and her husband own a $2.5 million home in Washington, and she is a partner in a family corporation that owns a share in her parents' New Orleans home. She has deep roots in the city as the daughter of a former mayor and the sister of the current one.
While Landrieu is registered to vote in New Orleans, she has used her Washington address on some official documents.
State Rep. Paul Hollis said he has not yet decided whether to appeal the decision.
Republicans clearly hope Landrieu's residency will be a campaign issue, however the legal fight is resolved. She has two Republican challengers, U.S. Rep. Bill Cassidy and Rob Maness, a retired U.S. Air Force officer backed by several Tea Party organizations.