A U.S. senator has scuttled President Barack Obama’s nomination of a pro-amnesty judge from his home state of Georgia in the latest skirmish over judicial nominees.

Citing Judge Dax Lopez’s work with an organization supporting amnesty for illegal immigrants, Sen. David Perdue, R-Ga., last week torpedoed Obama’s nominee to the U.S. District Court for Georgia.

In a press release, Perdue said he became “uncomfortable” with Lopez’s affiliation with the Georgia Association of Latino Elected Officials—an organization that the judge described “as very near and dear to my heart.”

Perdue blocked the Georgian’s nomination by withholding his “blue slip.” Under this longstanding Senate tradition, a senator effectively can veto a judicial nominee from his home state simply by refusing to recommend that person to the Judiciary Committee.

For 11 years, from 2004 to 2015, Lopez sat as a voting member on the board of directors of the Georgia Association of Latino Elected Officials. He held the position while serving as a judge on the State Court of DeKalb County beginning in 2010.

During his time on the board, the organization of Latino politicians supported Obama’s executive actions to allow millions of illegal immigrants to stay and work in America without being deported. The president’s widely criticized actions currently face a challenge at the U.S. Supreme Court.

In addition, the Georgia group regularly weighed in on local controversies.

In 2008, the Latino officials filed a joint lawsuit against the Georgia secretary of state, arguing that state law requiring voters to show identification at the polls unfairly burdened Hispanics.

Last year, shortly before Lopez stepped down from the board, the organization commended a local sheriff’s department for refusing to comply with deportation orders from federal Immigration and Customs Enforcement agents. In a press release, the group urged “other jurisdictions in the state to adopt similar policies.”

Perdue also voiced concern with “public comments” made by Lopez after he became a state judge. The senator did not specify the remarks he found troubling.

In a 2012 radio interview, however, the DeKalb County judge outlined steps that illegal immigrants, when detained, could take to avoid deportation. In addition to the advice, Lopez noted:

That’s not to say that you’re not vulnerable to being deported if you’re just living right and following the laws. Because you’re always vulnerable in a country like this.

Before Perdue’s blue-slip block, local legislators and law enforcement officials—including the state Senate’s majority leader and two county sheriffs—opposed Obama’s nomination of Lopez.

In an open letter in August, Cobb County Sheriff Neil Warren wrote that Lopez’s association with the Georgia Association of Latino Elected Officials suggested “a prejudice towards law-abiding citizens and law enforcement.”

But after Perdue blocked the nomination, liberal organizations opened a hailstorm of criticism in which they spotlighted Lopez’s Hispanic heritage.

The Hispanic National Bar Association dismissed concerns over Lopez’s association with the organization of Latino politicians. In a statement, association President Robert Maldonado wrote:

It is hard to fathom that we are in an era of such animosity that a judicial nominee’s participation in a trade association of bipartisan Latino elected officials is problematic …Our only inference is that he’s unacceptable to Senator Perdue because he is a Latino who believes in Latino participatory democracy.

If confirmed by the U.S. Senate, Lopez would become the first Latino judge to serve on a federal district court in Georgia.

In a statement, the Leadership Conference on Civil and Human Rights complained that “as long as men like Senator Perdue are the gatekeepers, it’s unlikely that one ever will.”

Born in Puerto Rico, Lopez attended Vanderbilt Law School, where he was a member of the Federalist Society, a conservative legal group. As a Republican, he enjoyed support from different corners of the GOP, from the Georgia Chamber of Commerce to conservative radio host Erick Erickson.

Perdue’s veto of Lopez comes as conversations continue among Senate Republicans about blocking all of Obama’s judicial nominees.

Some advocate freezing out all future nominees. Others argue that the nomination process already has become too political.

As a freshman senator who sits on the Judiciary Committee, Perdue has demonstrated a willingness to slow down the nomination process in certain circumstances. Last year, he opposed the confirmation of Attorney General Loretta Lynch.

Also last week, Perdue voted against confirming Judge Wilhelmina Wright for District Court of Minnesota after it came to light that she had written a law review paper characterizing President Reagan as a bigot. Wright won confirmation, 58-36.