In the movie Cat People, from 1942, a psychiatrist talks to the protagonist about what to do with his wife. The options were to nullify their marriage and be free to pursue his new love, or put his wife "away on observation and restraint" making him unable to divorce her:
The law is quite explicit, one cannot divorce an insane person.
I've always thought that insanity was grounds for divorce, or maybe back then it was the other way around. But later in the movie the psychiatrist tries to seduce his patient, so it might be that he wanted to push the husband into a divorce and clear his way.
So, was there really a law that prevented the divorce if the wife was put under restraint or it was just the psychiatrist ill-advising just to get the girl?