It's the federal courts version of the Hatfields and McCoys, but a move by one key U.S. senator could soon end the feud over a long-vacant judgeship on the U.S. Court of Appeals for the Ninth Circuit.

Democratic senators from California and Republicans from Idaho have quarreled for more than eight years over which state gets to propose a replacement for Judge Stephen Trott, who took senior status in 2004.

The dispute turns on where Trott worked: He was appointed to what had been considered a California slot on the Ninth Circuit, but chose to locate his chambers in Idaho. His spot represents the longest open vacancy in the federal judiciary. There hadn't been a nominee for the judgeship until President Barack Obama on August 1 named Washington native John Owens, a partner in the Los Angeles office of Munger, Tolles & Olson.

Enter Senator Patrick Leahy (D-Vt.), chairman of the Senate Judiciary Committee. Leahy thinks California deserves the seat. This month, he used the Senate tradition of the "blue slip" in a way that all but assures Owens' nomination will move forward through the confirmation process.

Leahy sent out "blue slips" for the nomination to the California senators, not to Idaho's, Democratic judiciary committee staff said. Leahy strictly adheres to this blue-slip process, which home-state senators use to block a nominee the White House wants to advance.

Here's how it works: If the home-state senators withhold the blue slips — actual pieces of paper for senators to sign approval for a nominee — then the nomination is dead in the water. By recognizing California as Owens' home state, Leahy stripped Idaho's senators of the power to use the blue slip to block Owens from a committee hearing.

So the possible solution to the long feud appears to be not much more complicated than Leahy's "choice of which set of home-state senators to recognize, and, surprise, he selected the two Democrats," said Russell Wheeler, a Brookings Institution fellow who studies the federal judiciary and the nominations process.

Idaho's senators are "evaluating their options" on the Owens nomination, a spokesman for Senator Mike Crapo (R-Idaho) said. "Senator Crapo was not consulted or informed of the nomination beforehand," spokesman Judd Deere said. "He is not happy with the nomination."

Senator James Risch (R-Idaho) said through a spokeswoman last week that he is "very disappointed with this appointment and there will be more to come of it."

Owens, who clerked for U.S. Supreme Court Justice Ruth Bader Ginsburg, was a federal prosecutor for 11 years in Washington and Southern California before joining Munger Tolles last year. He practices in white-collar criminal defense and investigations.

The California senators, Dianne Feinstein and Barbara Boxer, are expected to return the blue slips, supporting Owens. With that, the nomination, in the Democratic-controlled Senate, has a clear path to a committee confirmation hearing, a committee vote and then a chance to have the full Senate vote.

At that point, Owens' nomination might get tangled in the much broader and seemingly ever escalating Senate partisan battle over judicial confirmations. That feud, however, has its own political pressures.

LOOMING SHOWDOWN

The larger Senate dispute now appears headed toward a showdown over three nominees to the U.S. Court of Appeals for the D.C. Circuit. Republicans appear poised to filibuster those nominees, a move that conservatives still could employ to try to thwart Owens' nomination. Democrats, however, have threatened to change Senate rules if Republi­cans continue to block nominees.

The refusal to turn in blue slips, an indication that home-state senators do not approve of a court pick, has tripped up other nominees. Rosemary Marquez's nomination to the federal trial bench in Arizona and Elissa Cadish's nomination for a spot in Nevada did not advance for that reason. Neither pick got a confirmation hearing. Leahy even refused a request from Majority Leader Harry Reid (D-Nev.) to bend the blue-slip rules for Cadish.

The California senators have not made public statements about the Owens nomination. Leahy made his thoughts known in 2006, when then-President George W. Bush appointed N. Randy Smith to fill an Idaho-based vacancy on the Ninth Circuit.

"The practice in filling circuit vacancies has been to replace each with a nominee from the same state from which his or her predecessor was nominated," Leahy said then. "I do not know of any precedent for a judge's personal decision to change his or her personal residence resulted in shifting a circuit seat."

Contact Todd Ruger at truger@alm.com.