I don't believe so. But on the other hand, it's not like laws stop working if you don't use them.
Under Utah law, adultery is a class B misdemeanor (Utah Code 76-7-103), so conspiracy to commit adultery is a class C misdemeanour (Utah Code 76-4-202). So I think if a married person in Utah used the Ashley Madison website to arrange an affair, a Utah district attorney could justifiably charge Ashley Madison and/or its employees with conspiracy to commit adultery. Now, a class C misdemeanor, the maximum punishment is 90 days in jail (Utah Code 76-3-204), and a maximum fine of $750 for a natural person (Utah Code 76-3-301) and $1000 for a corporation (Utah Code 76-3-302) - so a DA might well decide it is not worthwhile. But, if they wanted to prove a point, I can't see why they couldn't bring the charges. Maybe if they had some personal connection to the affair; or maybe they might think the publicity would help their re-election campaign. Since Ashley Madison is based in Canada, I doubt Canada would agree to extradition - but if its employees or owners venture into the US, their extradition to Utah could be sought - intra-state extradition in the US is legally available even for misdemeanours. Now, if it all got this far, and further, the Supreme Court might decide laws against adultery are unconstitutional, but then again they might not decide that (or might refuse to hear the appeal). While I agree the story I'm telling here is somewhat unlikely to actually happen, I don't think there is anything legally impossible about it, and I'd call it somewhat unlikely rather than highly improbable.