The Ninth U.S. Circuit Court of Appeals rejected one challenge to Proposition 8 on Tuesday, but sought help from the state Supreme Court on another key issue that could decide the outcome of the case.

A three-panel judge on the appeals court ruled that Imperial County could not challenge a judge's decision that Prop 8, the voter-approved ban on same-sex marriage in California, is unconstitutional. In the ruling, the court said that marriage laws are a state matter.

The panel deferred another important question--if a ballot measure's sponsor has "standing" in court to defend it when state officials refuse--to the state Supreme Court. Normally, the state would defend a proposition in court. However, former Gov. Arnold Schwarzenegger and ex-Attorney General Jerry Brown declined to argue to uphold Prop. 8 and they did not appeal an August ruling by Chief District Court Judge Vaughn Walker declaring the ban unconstitutional. As a result, Protect Marriage, a conservative religious coalition that sponsored the 2008 measure, has been defending the same-sex marriage ban in court. 

It will now be up to the California Supreme Court decide if Protect Marriage has "standing", or the legal right to represent the interest of California and its voters. If the group does not, the federal court could uphold Judge Walker's ruling and re-instate same-sex marriage.

The appeals court is currently reviewing the constitutionality of the same-sex marriage ban. The court heard arguments last month for and against Prop. 8.

The state court has given no timetable as to when it will decide the question.

Read more from the San Francisco Chronicle here.