State laws against bigamy, same-sex marriage, adult incest, prostitution, masturbation, adultery, fornication, bestiality, and obscenity are likewise sustainable only in light of Bowers’ validation of laws based on moral choices. Every single one of these laws is called into question by today’s decision; the Court makes no effort to cabin the scope of its decision to exclude them from its holding. See ante, at 11 (noting “an emerging awareness that liberty gives substantial protection to adult persons in deciding how to conduct their private lives in matters pertaining to sex” (emphasis added)). The impossibility of distinguishing homosexuality from other traditional “morals” offenses is precisely why Bowers rejected the rational-basis challenge. “The law,” it said, “is constantly based on notions of morality, and if all laws representing essentially moral choices are to be invalidated under the Due Process Clause, the courts will be very busy indeed.” 478 U.S., at 196.2
http://supct.law.cornell.edu/supct/html/02-102.ZD.html