Just to be clear here, this case involved a police officer--Heffernan--who was demoted ostensibly on the order of the mayor of Paterson because the officer appeared to be supporting the mayor's opponent in an upcoming election (the officer was not actually doing that; he was at the opponent's campaign office to get a sign for his mother).
The officer filed suit against the city for infringing his First Amendment rights. He won a jury verdict but the judge had to recuse himself for conflict of interest and throw out the verdict. The next judge ruled against the officer. The decision was appealed to the 3rd Circuit which ruled as I detailed above, quashing three different arguments advanced by Heffernan (summary
here).
Understand that Heffernan was seeking relief for his unfair treatment based solely on his First Amendment rights being infringed.
Here's the code (1983, as Mark says). The issue, as I understand it, is whether or not the motive of the offending party is sufficient to allow a claim and therefore a redress. The 3rd Circuit said no, based on precedent and case law, the Supreme Court reversed the 3rd Circuit based on other case law. The Dissent followed the argument of the 3rd Circuit.
All that said, this decision is very narrow and very specific to this situation. Imagine, for a moment, that Heffernan did support the opponent and went to the campaign office to help. In such a situation, there is no question that he would have been deprived of his rights, according to the 3rd Circuit and to the SCOTUS, both the Decision and the Dissent.
But imagine instead that he was demoted because the mayor heard Heffernan was dating the mayor's ex-girlfriend, or he was demoted because he was seen at a Devil's game in a Ranger's jersey. In my mind, that would be every bit as wrong. Yet he'd have no recourse under this Federal statute, at all. And this is something that came up in the Q&A: could Heffernan have sought redress via the collective bargaining agreement that covered his employment or under other State laws? I think he could have and I'm not sure why he didn't, because having a petty little snot of a mayor like Paterson apparently has (had?) is not good and this kind of bullshit should be stomped out, whenever possible.
The point is, this decision isn't establishing new protections for public employees from retaliatory behavior at all. It's simply addressing this one somewhat unusual situation. And the city of Paterson is--imo--being run by complete idiots because this case has now cost the city
a boatload of jingle, far more than the original jury award of $100,000.