During the third and final day of his confirmation hearings before the Senate, Supreme Court nominee Neil Gorsuch was forced to defend his controversial opinion in a case that gun regulation advocates say prioritizes felons’ gun rights over safety.

Iowa Republican Sen. Chuck Grassley asked Gorsuch about United States v. Games-Perez, a 2012 case involving a felon convicted of possessing a gun without a serial number, which came before his Denver-based 10th Circuit Court of Appeals. While Gorsuch ultimately upheld the felon’s conviction, a separate opinion he wrote arguing against his own decision raised some eyebrows.

The defendant, Games-Perez, a felon caught in possession of a gun, was convicted of violating a federal law barring felons from “knowingly” having guns. But Games-Perez said he had no idea that he was a felon because, during his sentencing hearing, the judge was unclear about the status of his conviction.

Gorsuch and the other circuit court judges declined to overturn a lower court’s previous decision to convict Games-Perez. They determined that the word “knowingly” applied only to gun possession — not to being a felon. But Gorsuch also wrote an opinion arguing that the precedent set by those cases was wrong.

“The defendant said, ‘Well, hold on a sec.’ The word ‘knowingly’ is here — ’knowingly a felon in possession,’” Gorsuch explained in his hearing. “How does the word knowingly leap over the word ‘felon’ and only touch down at the word ‘possession’? It defied a bit of grammatical gravity, the defendant argued. And as a matter of plain meaning, I had to agree with him.”

Gun safety advocates point to that agreement as evidence of Gorsuch’s poor track record when it comes to gun safety, alongside a case where the 10th Circuit unanimously ruled that a convicted felon with restored civil rights could possess a firearm. On top of that, the National Rifle Association endorsed Gorsuch’s nomination to the Supreme Court.

“If you care about that for your children, he’s not your guy,” Pelosi said told a town hall on CNN in January. “Gabby Giffords’ group, the group for responsible solutions relating to gun safety, said that he comes down on the side of felons over gun safety.”

Robyn Thomas, executive director of the Law Center to Prevent Gun Violence, also disparaged Gorsuch’s track record on gun safety in a statement to Politifact.

“In his time on the 10th Circuit, [Gorsuch] made repeated efforts to weaken the federal law that’s prohibited felons from possessing guns for the past 50 years, a law that has saved thousands of lives and enjoys near-unanimous support among Americans and elected officials on both sides of the aisle,” she said.

Despite the criticism, Gorsuch stood by his opinion when Grassley pressed him on it during his hearing.

“I think notice is the key to the rule of law,” Gorsuch said, arguing that the court should pay attention to the words of the statute, not its legal history. “That the people can understand what’s expected of them, that the law is sufficiently clear, that before they’re put in prison for five or 10 or 20 years — and that’s what federal sentencing statutes require of judges in many, many cases — that we’re not putting them in prison on the basis of some secret law.”