New York, among other idiosyncracies in their family law, continues to have "fault divorce"; if you fail to prove fault, the court can refuse to grant a divorce.
I've been practicing my entire career in a "no-fault" state, and the idea that the state has some interest in telling someone who wants to get divorced, "No, even though you've filed a divorce, you must stay married..." strikes me as odd.
Odder still, however, is the following:
If your spouse engages in "egregious" conduct, a New York court can change the division of property to punish the "at fault" spouse. You might think that think that a court would have no hesitation in finding wife's affair, resulting pregnancy, telling husband that child was his (for four years) and a subsequent affair, taken together would rise to the level of "egregious" conduct and that wife had "deliberately embarked on a course designed to inflict extreme emotional or physical abuse upon" husband.
Apparently, you'd be wrong.
California has an explicit statute confirming that spouses have fiduciary duties to each other. This has, to date, been interpreted to mean that if one spouse secretly does funny business with the finances, the innocent spouse doesn't bear the risk of the funny business.
I had a similar "Surprise, you're not daddy!" case, briefly, years ago, and always wondered: would California have recognized my guy's claim for the breach of fiduciary duty?