http://legaltimes.typepad.com/files/utah-ssm.pdf
The State of Utah contends that what is at stake in this lawsuit is the State’s right to
define marriage free from federal interference. The Plaintiffs counter that what is really at issue is an individual’s ability to protect his or her fundamental rights from unreasonable interference by the state government. As discussed above, the parties have defined the two important principles that are in tension in this matter. While Utah exercise the “unquestioned authority” to regulate and define marriage, Windsor, 133 S. Ct. at 2693, it must nevertheless do so in a way that does not infringe the constitutional rights of its citizens. See id. at 2692 (noting that the “incidents, benefits, and obligations of marriage” may vary from state to state but are still “subject to constitutional guarantees”

. As a result, the court’s role is not to define marriage, an exercise that would be improper given the states’ primary authority in this realm. Instead, the court’s analysis is restricted to a determination of what individual rights are protected by the Constitution. The court must then decide whether the State’s definition and regulation of marriage impermissibly infringes those rights....
...After the nation’s wrenching experience in the Civil War, the people adopted the Fourteenth Amendment, which holds: “No State shall make or enforce any law which shall abridge the privileges and immunities of citizens of the United States; nor shall any State deprive any person of life, liberty or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.” U.S. Const. amend. XIV, § 1. The Supreme Court has held that the Due Process Clause of the Fourteenth Amendment applies to “matters of substantive law as well as to matters of procedure. Thus all fundamental rights comprised within the term liberty are protected by the Federal constitution from invasion by the States.”...
... [then quoting the Hon. judge Harlan II]
"[T]he full scope of the liberty guaranteed by the Due Process Clause cannot be
found in or limited by the precise terms of the specific guarantees elsewhere
provided in the Constitution. This “liberty” is not a series of isolated points
pricked out in terms of the taking of property; the freedom of speech, press, and
religion; the right to keep and bear arms; the freedom from unreasonable searches
and seizures; and so on. It is a rational continuum which, broadly speaking,
includes a freedom from all substantial arbitrary impositions and purposeless
restraints, . . . and which also recognizes, what a reasonable and sensitive
judgment must, that certain interests require particularly careful scrutiny of the
state needs asserted to justify their abridgement."