In Saltwater they cut it back to 2 per rod but there's a lot of grey area in that law. They will cite you for fishing multi hook rockfish ganions for rockfish but if you use small hook ganions for sand dabs they won't inforce it. Or at least I havn't seen it inforced for dabs. YOu can also get away with using a multi hook set up for snagging bait. I do believe freshwater is three hooks. You shouldn't feel guilty about using two hooks in fresh or salt. I fish a dropshot plastic above a bass jig some times and it works. If your releasing the fish and fishing artificial lures then I wouldn't consider it unethical and it's legal. Just my opinion some may feel differently.

JerryG