The following case decision suggests that such a clause would either not be enforceable or that the phrase "moral environment" would not be construed as excluding a live in boyfriend.
Howevever, there is no doubt that your ex could cause you some very expensive legal problems while litigating that issue until the courts decide.
Quoting Scott v Scott, 354 S.C. 118;579 S.E.2d 620 (2003)
RESTRAINING ORDER ON OVERNIGHT GUESTS
Father takes issue with the following provision in the divorce decree:
IT IS FURTHER ORDERED, ADJUDGED AND DECREED that all parties be, and are hereby, enjoined and restrained from having contact with a member of the opposite sex not related by blood or marriage in the presence of either child from the hours of 10:00 p.m. until 8:00 a.m. This injunction and restriction applies to any structure or open area where the children and the party will sleep in close proximity to each other.
Father argues that this restriction is overly broad and unreasonable. For example, he contends that if read literally, Caitlyn would not be allowed to have any girlfriends sleep over when Father has custody of Caitlyn. We agree.
The Court of Appeals struck down a similar provision in Jackson v. Jackson
, 279 S.C. 618, 310 S.E.2d 827 (Ct. App. 1983). In that case, the father was allowed to have his son visit only if the child was "not exposed to persons not related to [the father] by blood or marriage." The Jackson court explained as follows:
This restriction was intended to prevent the child from visiting in the presence of [the father's] live-in girlfriend. The restriction is overly broad and unreasonable as there was no finding that the presence of [the girlfriend] would adversely affect the welfare of the child. ... Even if this finding had been made, the restriction is overly broad in carrying out its intended purpose. Carried to its logical extreme, it would prevent the child from entertaining his own friends at his father's home.Id
. at 622, 310 S.E.2d at 829 (citation omitted).
The restriction in this case likewise is overly broad and therefore is reversed. Id.