A federal appeals court’s decision to overturn the convictions of former New York State Assembly speaker Sheldon Silver shows how public corruption cases have become much more difficult to substantiate in the wake of a Supreme Court decision narrowing what qualifies as corruption, legal analysts said.

In a 54-page opinion released Thursday, the U.S. Court of Appeals for the 2nd Circuit wrote that although prosecutors had presented enough evidence to justify Silver’s convictions, jurors had been wrongly instructed on the action Silver would have to take to make his conduct count as criminal public corruption.

The appeals court cited the Supreme Court’s decision in the case of former Virginia governor Robert F. McDonnell (R), who also had his convictions vacated in such a way that lawyers have long warned could have wide implications for others suspected of public corruption.

[Former New York Assembly speaker sentenced to 12 years in prison in corruption case]

“We recognize that many would view the facts adduced at Silver’s trial with distaste. The question presented to us, however, is not how a jury would likely view the evidence presented by the Government. Rather, it is whether it is clear, beyond a reasonable doubt, that a rational jury, properly instructed, would have found Silver guilty,” Circuit Judge Jose A. Cabranes wrote. “Given the teachings of the Supreme Court in McDonnell, and the particular circumstances of this case, we simply cannot reach that conclusion.”

To substantiate corruption charges, prosecutors must prove that the person suspected of wrongdoing performed an official act in exchange for some benefit. In the McDonnell case, the Supreme Court said that official act “must involve a formal exercise of governmental power, and must also be something specific” — effectively raising the bar on what constitutes corruption.

“Setting up a meeting, talking to another official, or organizing an event — without more — does not fit that definition of ‘official act,’ ” Chief Justice John G. Roberts Jr. wrote in the opinion.

Silver, 73, was convicted of taking millions of dollars in bribes and kickbacks in exchange for various favors and was sentenced to 12 years in prison — although he was allowed to remain free with his appeal pending. According to prosecutors, Silver, a lawyer, persuaded a doctor to pass on “valuable leads to unrepresented patients with mesothelioma,” and in return, routed grants to the doctor for research and gave other help. He also took actions, such as casting favorable votes, to benefit real estate developers that gave business to a law firm that then sent Silver kickbacks, prosecutors said.

[Feds: Ex-New York assembly speaker had affairs with lobbyist and another woman whom he recommended for a job]

Silver’s trial happened before the Supreme Court decided the McDonnell case, and jurors were given a broad definition of what “official act” he would have to perform to be guilty of corruption. They were told that such an act could be “any action taken or to be taken under color of official authority.”

The appeals court said because those jury instructions were wrong based on the McDonnell decision, the powerful New York lawmaker may have been convicted in error.

“Here, the instructions did not convey to the jury that an official action must be a decision or action on a matter involving the formal exercise of government power akin to a lawsuit, hearing, or agency determination,” Cabranes wrote. “Nor did the instructions prevent the jury from concluding that meetings or events with a public official to discuss a given matter were official acts by that public official.”

Legal analysts said the appeals court’s decision reinforces how prosecutors will face significant challenges in bringing and winning public corruption cases. Activity that may be uncouth — such as brokering meetings for wealthy benefactors — is now legal.

“It’s the legacy of Bob McDonnell — making life easier for corrupt public officials everywhere,” said Randall Eliason, a former federal prosecutor who teaches law at George Washington University

Joon H. Kim, the acting U.S. attorney in the Southern District of New York, said in a statement that prosecutors are “disappointed” by the decision, but “look forward to retrying the case.”

“Although this decision puts on hold the justice that New Yorkers got upon Silver’s conviction, we look forward to presenting to another jury the evidence of decades-long corruption by one of the most powerful politicians in New York State history,” Kim said. “Although it will be delayed, we do not expect justice to be denied.”

Former U.S. attorney Preet Bharara, who was in charge when Silver was convicted and sentenced, wrote on Twitter that the evidence was “strong” and that the Supreme Court had “changed the law.”

Steven Molo and Joel Cohen, Silver’s attorneys, said in a statement, “We are grateful the court saw it our way and reversed the conviction on all counts.”

Kelly Kramer, a white-collar criminal defense lawyer at the Mayer Brown law firm, said that Silver’s conviction had long been considered “one of the most vulnerable” after the Supreme Court’s decision on McDonnell. He said that although it is unlikely that many other convictions would be thrown out in a similar way, prosecutors probably will now bring fewer public corruption cases, knowing the high bar they must meet.

“What I think it means is there’s a lot of cases where there’s kind of inappropriate or unappealing behavior by politicians, and that kind of stuff isn’t going to get prosecuted unless the government can really point to a specific vote or funding grant or official action,” Kramer said.

Prosecutors will face one of their first major tests in the case against Sen. Robert Menendez (D-N.J.), who is accused of helping a Florida ophthalmologist with government business in exchange for campaign contributions and posh getaways. Menendez’s trial is scheduled to begin in September.

By prosecutors’ telling, Menendez tried to influence immigration-visa proceedings for the ophthalmologist’s girlfriends; assisted the ophthalmologist in a dispute with the Centers for Medicare and Medicaid Services; and advocated for action to help the ophthalmologist make money from a port security contract in the Dominican Republic.

Eliason said Menendez probably will not have the same success as McDonnell, although his attorneys have raised and will again raise the argument that he performed no official acts. And Silver, analysts said, may have similar trouble.

“He definitely sort of wins the battle,” Eliason said of Silver. “It remains to be seen whether he wins the war.”