Also, if infected with a sexually transmitted disease, it is important that one notifies the partner before sexual contact.
Sexual acts which are illegal, and often considered unethical, because of the absence of consent include rape and molestation.
Almost all modern systems of ethics insist that sexual activity is morally permissible only if all participants consent.
Sexual ethics also considers whether a person is capable of giving consent and the sort of acts they can consent to.
In many places in the world, people are not legally allowed to have sex until they reach a set age.
Feminists aim to redefine feminine sexuality in this world.
Throughout history, a whole range of consensual sexual acts, such as adultery, fornication, interracial or interfaith sex, 'sodomy' (see sodomy laws) have been prohibited; while at the same time various forced sexual encounters such as rape of a slave, prostitute, war enemy, and most notably of a spouse, were not illegal.
The criminalization of marital rape is very recent, having occurred during the past few decades, and the act is still legal in many places around the world.
Enthusiastic consent, as expressed in the slogan "Yes means yes," is typically the focus of liberal sexual ethics, rather than marriage.
Age of consent is also a key issue in sexual ethics.
Many practical questions arise regarding human sexuality, such as whether sexual norms should be enforced by law, given social approval, or changed.