Protection has been heightened for the three judges who ruled to maintain a block against President Trump's ordered travel ban.
CNN reports that the severity of the threats is unknown, but local police and the U.S. Marshals services have stepped up security.
The U.S. Marshal's service did not discuss the security measures taken, but said that they "take appropriate steps to provide additional protection when it is warranted."
As the nation awaits next moves from the White House in response to the court's controversial ruling, here is a look at the judges who served on the three-person panel.
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Judge William C. Canby Jr., appointed by President Jimmy Carter
Canby earned his undergraduate degree from Yale University in 1953, and later graduated from University of Minnesota Law School. The former JAG Corps lieutenant and Peace Corps professional later served as professor at Arizona State University, known for his authority on American Indian law.
Canby has presided over a number of crucial rulings throughout his career. A 1995 Canby ruling determined the Brady Handgun Violence Prevention Act -- which required local and state law enforcement officials to conduct background checks of handgun buyers -- was not in violation of the Tenth Amendment. The ruling was later reversed, though in the Supreme Court's decision in Printz v. United States.
In 2001, Canby wrote a unanimous panel decision holding that the Americans with Disabilities Act required the Professional Golfers Association to allow disabled golfer Casey Martin to use a golf cart when competing. The opinion was later affirmed by the Supreme Court.
Canby currently presides as a senior judge on the United States Court of Appeals for the Ninth Circuit, sitting in Phoenix, Arizona.
Judge Richard R. Clifton, appointed by President George W. Bush
Judge Richard Clifton was President George W. Bush's first appointment to the Ninth Circuit, nominated on Sept. 4, 2001.
Clifton received his undergraduate degree from Princeton University before graduating from Yale Law School. He clerked for Ninth Circuit Judge Herbert Choy upon graduation.
He then practiced privately in Hawaii before he was appointed to the federal bench. He notably served as one of the panel judges who upheld the imprisonment of Josh Wolf in 2006.
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Judge Michelle T. Friedland, appointed by President Barack Obama
Friedland is the most recently appointed panel judge, picked by President Obama on August 1, 2013. She received both her B.S. and J.D. from Stanford University, before notably serving as a law clerk to Supreme Court Justice Sandra Day O'Connor.
Before her confirmation, Friedland served as a litigation partner in the San Francisco office of Munger, Tolles & Olson LLP. During her legal career, Friedland represented a number of corporate clients in cases involving a wide range of legal issues, including antitrust, tax, patent, copyright, and consumer class actions. She also frequently represented the University of California in cases involving constitutional issues.
Although the president's verbal assaults on judges have drawn criticism, experts say his comments were not meant to put judges in danger.
"What he is doing is criticizing a judge for what he believes to be a failure to follow the law properly," Trump adviser Leonard Leo said about the President's remarks.
Trump has said he plans to appeal the court's decision to uphold the block on his travel ban and will be speaking with new Attorney General Jeff Sessions about the issue.
Josh King contributed to this report