Mississippi Sen. Cindy Hyde-Smith has announced that she will formally block President Joe Biden’s judicial nominee for the federal judgeship in the Northern District of Mississippi.

Biden nominated Scott Colom as his pick for the position in October and had gained support from Mississippi’s other senator Roger Wicker. Colom is the district attorney for the 16th circuit court district in Mississippi. He was elected to that position in 2015.

Hyde-Smith’s announcement on Tuesday puts Colom’s nomination in doubt thanks to a long-standing tradition in the U.S. Senate called the “blue slip” process, a tradition that gives senators a de facto veto over appointments to district court seats in their home states.

The tradition requires both home-state senators to return blue slips on a district court nomination before a confirmation hearing is set. Senators from both parties have used the move in the past to block judicial nominees from their states.

Hyde-Smith said in a statement that Colom is smart and well-liked in his district but said she was blocking his nomination because of support Colom has received from liberal billionaire George Soros. Soros reportedly provided almost $400,000 to a political action committee that backed the Colom’s campaigns.

Hyde-Smith said she is also concerned about Colom’s effort to oppose legislation concerning female athletes.

“As someone with a strong interest in protecting the rights of girls and women, I am concerned about Scott Colom’s opposition to legislation to protect female athletes,” the Hyde-Smith said in her statement.