They can only overturn it via Constitutional Amendment. Veto Power doesn’t apply
from Thomas’ dissent
The majority’s decision today will require States to issue marriage licenses to same-sex couples and to recognize same-sex marriages entered in other States largely based on a constitutional provision guaranteeing “due process” before a person is deprived of his “life, liberty, or property.” I have elsewhere explained the dangerous fiction of treating the Due Process Clause as a font of substantive rights. McDonald v. Chicago, 561 U. S. 742, 811–812 (2010) (THOMAS, J., concurring in part and concurring in judgment). It distorts the constitutional text, which guarantees only whatever “process” is “due” before a person is deprived of life, liberty, and property. U. S. Const., Amdt. 14, §1. Worse, it invites judges to do exactly what the majority has done here—“‘roa[m] at large in the constitutional field’ guided only by their personal views” as to the “‘fundamental rights’” protected by that document. Planned Parenthood of Southeastern Pa. v. Casey, 505 U. S. 833, 953, 965 (1992) (Rehnquist, C. J., concurring in judgment in part and dissenting in part) (quoting Griswold v. Connecticut, 381 U. S. 479, 502 (1965) (Harlan, J.,concurring in judgment)).
By straying from the text of the Constitution, substantive due process exalts judges at the expense of the People from whom they derive their authority. Petitioners argue that by enshrining the traditional definition of marriage in their State Constitutions through voter-approved amendments, the States have put the issue “beyond the reach of the normal democratic process.” Brief for Petitioners in No. 14–562, p. 54. But the result petitioners seek is far less democratic. They ask nine judges on this Court to enshrine their definition of marriage in the Federal Constitution and thus put it beyond the reach of the normal democratic process for the entire Nation. That a “bare majority” of this Court, ante, at 25, is able to grant this wish, wiping out with a stroke of the keyboard the results of the political process in over 30 States, based on a provision that guarantees only “due process” is but further evidence of the danger of substantive due process.
>> They can only overturn it via Constitutional Amendment. Veto Power doesn’t apply <<
Yes and no.
In the first place, not all SCOTUS rulings involve the Constitution. Many are simply interpretations of statutes. The Congress certainly can overrule SCOTUS in such matters, but then veto power of POTUS can subsequently overrule the Congressional act.
In the second place, the Constitution gives Congress the power to define the jurisdiction of the Federal courts. Therefore, it’s conceivable that even on a constitutional matter, Congress could limit the jurisdiction of all Federal courts. For example, Congress could pass a law that says no Federal court, including SCOTUS, shall have any jurisdiction over any state law that defines, regulates or otherwise deals with marriage. But then, such a Congressional action would again be subject to a POTUS veto.