@PotomacBob
If that's true, why would any company adopt such policies? I
Such lawsuits are groundless. As long as the company has plausible deniability (the exec at least tried to hide the affair) the company doesn't have a responsibility to ensure nobody violates the policy, they just have to take action when the policy is violated. Usually, the 'appropriate' response is to fire the lower-ranked employee and place some sort of 'official reprimand' in the executive's personel file.
But there's plenty of reasons for such a policy. For example, when a executive's dalliances become too public knowledge, in order to protect him the other half of the affair can be quietly fired for violating the policy, slapped with a gag order in order to keep her severance package, or in a large enough company just be reassigned to a location on the other side of the country. Or picture a family-owned firm - to scare golddigger employees from trying to marry into the family, any that go on a single date with the boss's son get fired before there's any connection. Other reasons have also been mentioned. There's probably a few more.