To answer this, you have to understand what government is. Government is a group of society to benefit society. The way that is structured varies. The efficiency too varies. When government does not act in society's interest, but rather in it's own interest, there is a failure.
Based upon that, I would say that parents have a responsibility to teach their children morals and laws in accordance with being a good citizen. Government should encourage this. In some cases, parents need education. Sad but true. Sex regulation should be confined to illegal sexual acts. Legality is determined by predominant morals of society. Government should encourage research. After all, that's the biggest source of money.
Lastly, it can be dangerous. There are some couples who literally become criminals when visiting another state or changing residence. Personally, I don't want the police in my marriage bed.