I wrote a post ages back on the old laws that protected marriage.
“Protection from adultery is the crucial means of safeguarding marriage for future generations.”
Protection from cheats is one.
Marriage is a contract. Yes, you should be held to your oath of monogamy.
Holding the seducer responsible doesn’t divide the house.
Also counts under criminal conversation. “Open marriage” cucking is effectively already illegal.
Way more expensive than a hooker.