Oh, dunno about NJ/RI but in OH there've already been several petitions started by this or that group to get it outlawed over the past few decades (at least, probably longer), since we value personal freedom here it's always been voted no and in the past 10-15 years they haven't even gotten enough signatures to get it on the ballot for election day, as the majority here feel it's pointless to even try to govern what 2 consenting people are allowed to do in their own bedrooms, particularly after gay marriage was legalized. Free love and all that. That kinda goes along with the AOC still being 16 here still with no age gap considerations at all as it's been since 1929. There's just no political will to change what still works/isn't broken.
As far as incest risks, whatever they are, not my problem or business and that's between the siblings considering it and most in OH see it that way. The reasearch I've uncovered on bored/curious days says it's around +3% for even the most common genetic disease, Down's Syndrome (normally 1 in ~700, so 1 in 30 of siblings having a Downs baby, still low, unless they plan on having 30 kids or something), and just goes down from there, with the caveat being that their is no history of it like the Hapsburgs (ie parents, grandparents, etc are all vanilla). Really though even the worst possible incest situation than even the Hapsburgs (and even that took 500+ years before it caused sterility and 200+ before diseases bad enough to cause deformities were showing up) I can think of was around 70-74k years ago when the Toba eruption wiped out all but 10k breeding pairs of humans worldwide, most of which were families/tribes stuck in isolation for the better part of a century until the volcanic winter finally let up. Imagine that, 4-6 generations of not just the current ~2% of the population impregnating their family but more like 50%, and in all sorts of combos, incuding the far-riskier-than-siblings intergenerational (fathers/daughters, mothers/sons) since it was mostly either breed with family or watch everyone die out (probably of horniness first rather than old age, like Brooke Shields and her brother would have on that island in Blue Lagoon, but I digress). Now, I can't find too many specific examples of individuals from that period with genetic diseases, presumably there were quite a few from daughters getting knocked up by their dads and mothers by their sons, but if what was left of the human race can survive ~100 years of that (albeit with everyone alive today with genetic "scars" from it) I'm not at all worried about today's 2% incest rate enough to go into a panic and call Columbus and beg them to outlaw it before the human race goes extinct (it wouldn't stop them anyway, like gays did in the 1960's and before they'd just keep it secret and most of them do so anyway due to the social stigma of it). I just have better things to do with my life and so does everyone else, even if it's just fapping to incest porn/AVNs. Besides, it's 2024, there's genetic screening these days for those siblings that wanna make some babies but also want to minimize the risks instead of just going in blind and crossing their fingers. There's also even talk about using Crispr to fix any abnormalities in the zygote that may show up if they are unlucky, but that tech isn't here yet (maybe 2030's, and it's related to the "designer babies" debate). I leave with a quote from Quora (mostly experts on variious topics/fields there if you know who's posting) "A brother and sister can have a perfectly healthy child together. Children born of incestuous couplings do have an increased risk of presenting genetic defects and/or deformities. But the increased risk is negligible with first generation inbreeding. It only becomes a significant risk with multi-generational incest."
I can't imagine there are any laws explicitly protecting incest or else someone would have cynically based a political campaign on overturning them already and the publicity would have forced those states to immediately put aside more important legislation to change them.
