He is not he didn't have a say. The only way to get responsibility is to have power over the situation.
Its her decision alone its her responsibility alone. Can he opt in? Yes he can. Is it the right and sensible thing to do? Yes again but to make it mandatory by law well that is as asinine as blaming rape victims.
You can call it a necessary evil at best. Its utterly unfair.
It gets absolutely ridiciulous when you factor in that woman can even opt out with a simple lie even after pregnancy.