The more-developed constitutional precedent on procreative rights offers some settled principles but also frames still-debatable issues that presage more-recent arguments over gay rights.
Procreative rights: the established precedent and open questions.
Transcending the myths focuses discourse by excluding illegitimate points. Justice Douglas's Griswold holding that "privacy" protected marital contraception provoked both valid and illegitimate challenges. Myth-induced critiques obsessing on the constitutional text's lack of the word "privacy" were disingenuous, since text cannot limit inalienable rights. Genuine debate, instead, involved other issues--including how Douglas used extra-textual principles to identify the right. He claimed to proceed incrementally, following both analogous precedent, such as longstanding holdings on parental rights, and rights expressed in constitutional text, such as association and the right against unreasonable searches.
And Douglas provoked further criticism with a metaphor describing how unenumerated rights are tethered to recognized rights, a metaphor ridiculed in popular media. He said rights expressed in constitutional text had "emanations" casting "penumbras" containing more-general rights, such as privacy. That rhetorical flourish may have been imprudent but should not taint his underlying analysis. His descriptive language aside, Douglas had grounded his interpretation in text and precedent. More-valid critique focuses on whether he took that process too far--whether he properly declared a general right of privacy rather than only a narrower right of marital procreative autonomy.
In general, courts legitimately may use some extra-textual sources to determine whether a claimed inalienable right exists. Debatable issues, instead, include the appropriate types and relative weights of those extra-textual sources; the ways to apply them to articulate rights without undue judicial discretion; and conclusions that should follow from applying those sources and methods about the existence, nature, and scope of rights protected--all still difficult, remaining questions.
Public debate about abortion also illustrates the distinction between fair and irrelevant issues for argument. A genuine critique of Roe (refined by Casey) cannot merely complain the text lacks the term "abortion." And basic reproductive freedom and women's bodily autonomy at least reflect principled implications of Griswold, other precedent, and text--even if one contests the formulation and application of those principles. Most legitimately disputable is the competing scope of states' asserted interests in pregnant women's health and fetal "life," the rationale allowing states to ban most abortions after fetal viability. Genuine debate continues on the nature and limits of those interests and their relation to a woman's rights.
Conservative: Granted there are unenumerated rights, but declaring a right to control procreation displays too much discretion by judges.
Whole Constitutionalist: The Court recognized women's reproductive and bodily autonomy in a process yoked to text, history, and precedent. At the same time, it has recognized states' interest in the fetus, allowing bans of most post-viability abortions --following a common law, rather than either a religious or secular-moral, view of whether and when fetal "life" becomes comparable to born human life.
Freed from the obfuscation of myth-based thinking, the above dialogue could continue productively. (Note Conservative's interlocutor is now Whole Constitutionalist, reflecting this essay's perspective.)
The whole-constitutionalist perspective on gay rights.
Attuned to the Court's approach to such other rights issues, gay marriage advocates present two independent constitutional arguments. The first relies on more-explicit text, the Equal Protection Clause: "No state shall . . . deny to any person within its jurisdiction the equal protection of the laws." On its face, that text could be read to prohibit states from denying gays a legal right afforded heterosexuals--the right to choose a marriage partner corresponding to one's sexual orientation.
But equal protection precedent calls for a more-constrained analysis. To uphold most classifications that treat groups of people differently, the Court has required only a rational basis. Thus, the class of speeding drivers can be made to pay a fine others do not because highway safety is a legitimate government goal to which such fines are rationally related. The government has been required to meet a higher level of justification, heightened scrutiny, only for certain classifications: those related to the Equal Protection Clause's original motivation--racial classifications--and those of certain other groups who have been held to somehow have diminished political power.