The start of the decision is a pretty good summary
https://www.supremecourt.gov/opinions/19pdf/18-1059_e2p3.pdf
During former New Jersey Governor Chris Christie’s 2013 reelection campaign, his Deputy Chief of Staff, Bridget Anne Kelly, avidly courted Democratic mayors for their endorsements, but Fort Lee’s mayor refused to back the Governor’s campaign.
Determined to punish the mayor, Kelly, Port Authority Deputy Executive Director William Baroni, and another Port Authority official, David Wildstein, decided to reduce from three to one the number of lanes long reserved at the George Washington Bridge’s toll plaza for Fort Lee’s morning commuters.
To disguise their efforts at political retribution, Wildstein devised a cover story: The lane realignment was for a traffic study.
As part of that cover story, the defendants asked Port Authority traffic engineers to collect some numbers about the effect of the changes. At the suggestion of a Port Authority manager, they also agreed to pay an extra toll collector overtime so that Fort Lee’s one remaining lane would not be shut down if the collector on duty needed a break. The lane realignment caused four days of gridlock in Fort Lee, and only ended when the Port Authority’s Executive Director learned of the scheme. Baroni and Kelly were convicted in federal court of wire fraud,fraud on a federally funded program or entity (the Port Authority), and conspiracy to commit each of those crimes. The Third Circuit affirmed.
Held: Because the scheme here did not aim to obtain money or property, Baroni and Kelly could not have violated the federal-program fraud or wire fraud laws.
And the end of the decision is
“We therefore reverse the judgment of the Court of Appeals and remand the case for further proceedings consistent with this opinion. “
Which I assume means they can retry them with the correct charges this time.