Judges should adjudicate from the bench -- decide matters in dispute. To "legislate from the bench" would be judges creating laws -- the province of the legislative branch, not the judiciary. It's certainly true there's a blurry space there, and when courts make decisions that may be interpreted as the equivalent of manifesting new law, you'll hear complaints about "legislating from the bench".
> It's certainly true there's a blurry space there
It's trivial to determine if the court has "legislated from the bench" though: do parties unrelated to the lawsuit in question immediately, after the decision, have to behave substantially differently? Do extremely large numbers of people have to behave substantially differently after the decision?
If they do, that's "legislating from the bench." That's literally the test.
When they don't, a decision only affects the people in the suit and similar situations going forward (precedent). That's just the normal, everyday action of the judiciary branch. It's still "policy" (broadly speaking), but it's not legislating.
In the most recent case, changing literally every Title IX program, overnight—as well as all employment scenarios nationwide—is clearly "legislating from the bench", since it a) applies with immediate effect to large numbers of people not party to the suit, and b) requires them to behave substantially differently than they had before the decision.
(I'm fine with "legislating from the bench", BTW, that's literally how Civil Rights legislation is intended to work. Congress passed responsibility to the courts, just like in other areas they've passed responsibility to the executive branch.)
If a law is passed and people wait 40 years to enforce it(but then it's hot-topic and so will be enforced widely), is it "legislating from the bench" for the court to enforce a law that already exists?
It's literally the first criteria that to count as new legislation, the effect must be immediate:
> do parties unrelated to the lawsuit in question immediately, after the decision, have to behave substantially differently?
The court has not argued in their decision that Congress meant to provide these protections—they explicitly only argued that the law can be (re-)interpreted today as allowing it (using a broad interpretation). They fully admit that Congress at the time did not expect it to be interpreted this way.
That's the "legislating" part of "legislating from the bench": the actual legislators who voted on the original legislation did not intend to cause this behavioral change on ~200M Americans (at the time it was passed). 40 years later, the courts made the decision to legislate that behavior, from the bench.
Personally, I have to admire that kind of Chutzpah—no one will accuse today's court of lacking the will to power. That one of Trump's "conservative" justices wrote the decision is the icing on the cake. :)
You don't have to do such hypothetical backflips when you can see that the entire response of a huge group of people to Roe v. Wade has been to force the judiciary to legislate from the bench (with varying success).