Laws to protect adults from coercion, children from sexual exploitation, and the public from offensive behavior are justifiable. However, many laws against sexual conduct originated in a desire to promote public morality and perpetuate sexism, and it is hard to justify them.

The laws governing sexual conduct include laws against crimes of exploitation and force (such as rape, carnal knowledge of a juvenile, and child molestation), against various consensual acts (such as fornication and adultery), against gays and lesbians, against offending public taste (exhibitionism, voyeurism, solicitation, disorderly conduct, lewdness, and the like), against behaviors involved in reproduction (contraception and abortion), and against criminal commercial sex (notably prostitution and obscenity). These laws are often capriciously enforced, and this unequal enforcement has high social costs that may require reform.

Certain trends can be discerned in the reform of such sex laws. The American Model Penal Code included proposals to decriminalize consensual sexual behavior. The legal principle that has accounted for much court action to reform laws against contraception and abortion is the right to privacy. The constitutional principle of equal protection has been used to combat discrimination against groups identified by their sexual conduct, including gays, lesbians, and commercial sex workers. A factor that has influenced legislators is the movement for the decriminalization of victimless crimes; recently, however, critics have challenged the argument that no one is harmed by prostitution or adultery. The issue of pornography and obscenity, which includes such problems as definition, conflicting societal values, and actual demonstration of effects, is a confusing one. The latest controversy is over the availability of X-rated goods and services on the Internet. Abortion remains a volatile and highly controversial matter.

Sex-law reform moved more slowly in the 1990s and early twenty-first century than it did in the previous decades, and there are signs of a conservative backlash. In the future, the law will need to balance individual rights and the public interest when it comes to issues such as AIDS and new reproductive technologies.