(Bloomberg) -- US Supreme Court justices signaled they will put new limits on public-corruption prosecutions as they considered overturning the conviction of a onetime top aide to former New York Governor Andrew Cuomo.

Hearing arguments in Washington Monday, the justices questioned whether Joseph Percoco could be convicted of so-called honest-services fraud given that he was working for Cuomo’s re-election campaign -- and not the government -- during a key eight-month period in 2014. The Biden administration is defending the conviction.

Justices from across the court’s ideological spectrum said they worried the administration’s position would put influential lobbyists -- and those who hire them -- at risk of prosecution. Chief Justice John Roberts described the government’s arguments as “an effort to break down the concept of political power.”

The court has narrowed the reach of federal corruption laws in recent years, tossing out the convictions of former Virginia Governor Bob McDonnell in 2016 and two allies of former New Jersey Governor Chris Christie for the George Washington Bridge lane-closing scandal in 2020.

The court on Monday is also considering the fraud conviction of Louis Ciminelli, whose Buffalo, New York, firm won a $750 million development contract after he took part in what prosecutors said was an effort to rig the bidding criteria.

Percoco was accused of accepting bribes in exchange for helping one company obtain a state power contract and another get a construction contract without having to first negotiate a labor peace agreement. A federal jury in Manhattan convicted him under a statute that bars schemes that deprive the public of “the intangible right of honest services.” He was sentenced to 6 years in prison.

Percoco says his prosecution ignored a crucial distinction between government officials and private lobbyists. He contends that private citizens aren’t bound by any duty to act in the public interest.

The Biden administration is defending Percoco’s conviction, arguing that he was functionally still serving in his role as Cuomo’s executive deputy secretary, working out of his government offices and issuing instructions to the governor’s staff. Percoco formally returned to the job a month after Cuomo was re-elected.

In questioning the conviction, Justice Clarence Thomas pointed to the absence of a state prosecution of Percoco.

“It seems as though we are using a federal law to impose ethical standards on state activity,” Thomas said.

The case is Percoco v. United States, 21-1158.

(Updates with excerpts from argument starting in third paragraph.)

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