I think that for the cases that you are thinking about such a law would function, eventually, as a sanctionatory law but not as preemptive.
When we read the testimonies of so many that have been forced to those inhumane acts we see that, at the time of its occurrence, those people where unable to fight back the pressure put upon them. How could a law be applied if, almost certainly these people would keep quiet?
However I think it is important that such a cover for the right to give life to a new being exists.
that is a very VERY good and exceedingly important question and, as one might suspect and as particularly serious readers familiar with my writing will presume, i have given much thought to that question and have much to say
i believe intelligent readers of this thread will be mostly pleased with what i will say and that many will anticipate much of the specific detail