§1. If either of the spouses causes grave mental or physical danger to the other spouse or to the offspring or otherwise renders common life too difficult, that spouse gives the other a legitimate cause for leaving, either by decree of the local ordinary or even on his or her own authority if there is danger in delay.
§2. In all cases, when the cause for the separation ceases, conjugal living must be restored unless ecclesiastical authority has established otherwise.
Source: Code of Canon Law (Vatican.va)