[natbobc]

Better approach in my mind is to develop vaccines.

Last I checked marriage is by no means an STI preventing form of contraception so I think you mean monogamous relationship. As many people are in happy monogamous relationships with no intent for marriage because of a variety of reasons.

It's not entirely clear to me how you would even go about enforcing such a law. Why would either participant report their "crime"? Isn't that effectively what Judeo-Christian beliefs have encouraged since their inception?