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

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. :)