This situation is a bit of a grey area I think.
Think of it like this: a person has got something that a few people want, or might want.
They offer it to one person, that person is dead pleased, says yes please - and the person agrees they can have it, no holds barred. the deal is done.
The same person then offers that object to someone else, despite the fact it's already been given to the first recipient.
The second recipient accepts and takes the item. now this person knows it actually belongs to the first recipient - so in theory they ought to say no. It all depends whether you think the offerer has still got the rights to the object despite having given it to someone before.
I think that is why it's hard to judge. You could say the OW is accepting stolen goods, although she is not the one doing the stealing. You can be charged with this in a property situation but not in an emotional one.
There again, you could argue that the offerer is not taking back the same thing he originally gave away, in order to re-offer it, but actually offering another item the same as the initial one. It does however detract from the initial thing, obviously - the first recipient loses out big time.
Accepting stolen goods is a lousy thing to do, but stealing them in the first place is less moral still.
So. Does a husband have the right to his love once he has chosen to give it to his wife? Can he then ask for it back?
I wish I knew the answer to that.