Thirty-eight states have laws in place that relate to adultery. Though criminal laws against adultery are not frequently enforced, the network of criminal laws, tort laws, and domestic relations laws related to adultery disincentivize extra-marital sex, an effect heightened by the stigma and other social attitudes associated with adultery. This essay argues that the socio-legal state of affairs concerning adultery is bad for marriages (and similar relationships), bad for public health, and is simply bad public policy. This is the case, in no small part, because the law treats infidelity -- having sex with someone other than your primary partner without his or her consent or knowledge -- and consensual non-monogamy in the same manner. In fact, infidelity and consensual non-monogamy are significantly different ethically, psychologically, and practically, a claim buttressed by social scientific research. In contrast to proposals to abolish laws that disincentivize adultery whole cloth, this essay argues for more nuanced set of reforms that would end the negative treatment of consensual non-monogamy while leaving unchanged laws relating to infidelity.