Federal prosecutors have taken it on the chin in recent U.S. Supreme Court decisions that pushed back against the government's expansive reading of federal criminal laws. The latest setback came Thursday, when a federal appeals court voided the corruption conviction of a once-powerful New York state Assembly speaker.

The U.S. Court of Appeals for the Second Circuit said the jury in that case might not have convicted the lawmaker, Sheldon Silver, had they been instructed properly on the justices' narrow definition of “official act” in the context of prosecutions for honest services fraud.

That narrowed definition was adopted by a unanimous Supreme Court in the June 2016 decision in McDonnell v. United States, the most recent of a chain of rulings that cabined prosecutors' use of often broadly worded criminal provisions. Prosecutors plan to retry Silver.

“Regardless of what happens with Sheldon Silver upon retrial, the Second Circuit's opinion, on top of the Supreme Court's unanimous decision in McDonnell, nonetheless sends perhaps more than just a cautionary tale to prosecutors about overreaching in political corruption cases,” Lathrop Nelson III of Montgomery McCracken Walker & Rhoads wrote on his white-collar blog. “There indeed is a line between what is an improper quid pro quo and acts that constitute constituent services that we expect our elected officials to perform.”

Here's a snapshot of the McDonnell decision and other rulings—four of which were issued by the Roberts Court—that restricted prosecution offices.

'Tawdry Tales' (McDonnell v. United States)

Former Virginia Gov. Robert McDonnell, represented by then-Jones Day partner Noel Francisco, was indicted on honest services fraud and Hobbs Act extortion charges related to his and his wife's acceptance of $175,000 in loans, and other benefits from a Virginia businessman while the governor was in office. To convict them—his wife was also charged—prosecutors had to show the governor committed, or agreed to commit, an “official act” in exchange for the loans and gifts.

“There is no doubt that this case is distasteful; it may be worse than that,” wrote Chief Justice John Roberts Jr. “But our concern is not with tawdry tales of Ferraris, Rolexes, and ball gowns. It is instead with the broader legal implications of the government's boundless interpretation of the federal bribery statute. A more limited interpretation of the term 'official act' leaves ample room for prosecuting corruption, while comporting with the text of the statute and the precedent of this court.”

Criminal defense lawyers and others had predicted the ruling would reach beyond public corruption cases to all federal bribery cases and potentially force prosecutors to prove a quid pro quo in insider trading cases. However, others have argued the decision isn't as broad as some said.

“The reality is that McDonnell is of limited significance: It prevents prosecutors from bringing only the weakest of public corruption cases, those where the prosecution lacks even circumstantial evidence that a corrupt payoff was for something more than a chance to meet with the public official,” Covington & Burling lawyers Arlo Devlin-Brown and Erin Monju wrote in this piece at the New York Law Journal.

'Mad Prosecutors' (Yates v. United States)

After a federal agency discovered that a commercial fishing vessel had captured undersized red grouper in violation of conservation regulations, the owner ordered his crew to throw them overboard in an attempt to evade the violation. The owner was charged with violating a provision of the Sarbanes-Oxley Act that prohibited, among other things, the knowing destruction or alteration of any record, document or tangible object with the intent to obstruct a federal investigation.

Were the fish “tangible objects” under the law? During arguments, the late Justice Antonin Scalia asked, “What kind of a mad prosecutor would try to send this guy up for 20 years?”

Justice Ruth Bader Ginsburg, writing for a 5-4 majority in 2015 said: “The words of Section 1519, the government argues, support reading the provision as a general ban on the spoliation of evidence, covering all physical items that might be relevant to any matter under federal investigation. We resist reading Section 1519 expansively to create a coverall spoliation of evidence statute, advisable as such a measure might be. Leaving that important decision to Congress, we hold that a 'tangible object' within Section 1519's compass is one used to record or preserve information.”