Despite a major setback at the U.S. Supreme Court, the National Organization for Marriage (NOM) is pressing ahead in its fight to overturn a federal judge's order making Oregon the 18th state to allow gay and lesbian couples to marry.

On May 19, U.S. District Judge Michael McShane struck down the state's ban and Oregon officials, who sided with plaintiffs, immediately implemented his order.

On Wednesday, the group asked the full Ninth Circuit Court of Appeals in San Francisco to reconsider a 3-judge panel's decision rejecting the group's attempt to intervene in the case.

NOM has faced a string of losses in the case. McShane denied NOM's last minute request to intervene in the case, the Ninth Circuit denied NOM's request to stay proceedings in the case or stay the ruling and the U.S. Supreme Court denied the group's request to set aside the ruling as it seeks to intervene in the case.

“[R]ehearing en banc is warranted … because the issues presented by this case are of 'exceptional importance,'” NOM said in its latest filing. “Indeed, the constitutional issue addressed in the underlying judgment is arguably the most contentious issue to have been addressed by the courts in forty years. The supposed jurisdictional barriers are also of exceptional importance, for they are already providing an incentive for 'friendly' suits that is threatening the very adversarial nature of our system of justice.”

On Monday, a Ninth Circuit panel heard arguments in three cases challenging similar bans in Hawaii, Nevada and Idaho. A ruling in favor of the plaintiffs could make NOM's case moot.

(Related: Ninth Circuit panel “skeptical” of arguments in favor of state bans on gay marriage.)