"Circuit division would have a devastating effect on the administration of justice in the western United States," Chief Circuit Judge Sidney Thomas said in prepared remarks to the House Judiciary Subcommittee on Courts, Intellectual Property and the Internet. He said a split would "increase delay, reduce access to justice and waste taxpayer dollars."
There have been attempts in both the House and Senate to split the 9th Circuit and create a new 12th Circuit.
A bill introduced in January by Sen. Jeff Flake, R-Ariz., would carve out Arizona, Nevada, Washington, Idaho, Alaska and Montana for a new "mountain circuit." The 9th Circuit would be left with the three Pacific states, the Northern Mariana Islands and Guam.
The left-learning 9th Circuit is currently the largest of thirteen courts of appeals. More than half of its 29 judges have been appointed by Democrats, and it covers nine states, two territories and over 65 million people.
Flake and other Republican lawmakers have argued it can take up to 15 months for the court to hand down a decision. Nicknamed the "9th Circus" by conservatives, many of its rulings have also been overturned by the U.S.Supreme Court.
Calls for breaking up the 9th Circuit have gained traction in recent weeks after it ruled last month that President Trump's original travel ban executive order was unconstitutional. Trump immediately disagreed with decision and called into question the judges' impartiality.
On Wednesday, District Judge Derrick Watson of the 9th Circuit in Hawaii then blocked key parts of Trump's new order, which bansimmigration from six majority-Muslim countries. The 9th Circuit also said it would not rehear the case regarding the original order.
Circuit Judges Carlos Bea and Alex Kozinski agreed with Thomas' testimony that the 9th Circuit should be left alone. Bea, who was appointed by former President George W. Bush, said it is important that their jurisdiction oversees as much as it does, because it minimizes the risk that law differs across Western-area cities.
"A decision by our Court binds courts and litigants in the whole Western area," Bea said, using the law of intellectual property as reason to keep the jurisdiction together. "This minimizes the risk that the law of intellectual property — copyrights and trademarks, for instance — maritime trade, labor relations, employment discrimination, for instance — will be different in Phoenix, San Francisco or Seattle."
It is not unheard of for a large circuit court to split up. In 1929, the 8th Circuit was split to deal with a booming population in the area.
But Democrats on Thursday accused Republicans of attempting to engage in "judicial gerrymandering."
"Like clockwork, we see proposals to split up the 9th Circuit whenever it delivers a controversial decision with which conservatives disagree," Rep. Jerrold Nadler, D-N.Y., told the subcommittee. "Just as there is a nationwide movement to end legislative gerrymandering, we should resist this form of judicial gerrymandering as well."
Rep. Jason Chaffetz, R-Utah, strongly countered Nadler, calling 9th Circuit rulings as of late "infuriating."
"To look to the 9th Circuit, to see people say, 'Well there's 70 people here we have to protect and 80 people here,' what about protecting the United States of America?" he said. "It's the 9th Circuit that is causing these problems and taking away the duties that the Judiciary Committee, the Congress has given to the President of the United States to protect our borders."