"If my pubescent friend can shoot more than blanks then it is my obligation to make sure no pregnancy results. No argument from me here, either. I would be jailed if that were to happen."

You would - but you shouldn´t. If you are jailed, who has to care for your child? One option is your pubescent child. So if it were to happen, you should stay at liberty and work to support the new child, and not burden the child father with it. And your obligation is (or ought to be) not to make sure that no pregnancy results, but to make sure that you are willing and able to care for the new child without burdening the child father. Or yes, make sure no pregnancy results if you do not feel you can provide for your new child to your satisfaction.