The U.S. Supreme Court, by a 6-3 majority in the Medellin v. Texas decision, struck a significant blow for the U.S. Constitution and U.S. sovereignty against the encroaching power of international treaties and U.N. authority upon U.S. law.
Contrary to much of the reporting in the media, the Supreme Court decision in Medellin v. Texas was not primarily either a death penalty case or a decision regarding presidential executive power.
Both Chief Justice John Roberts’ majority opinion (joined by Justices Alito, Kennedy, Scalia and Thomas) and Justice Breyer’s dissent (joined by Justices Souter and Ginsburg) make it clear the justices understood the Medellin case to be about the scope and authority of international law in domestic U.S. courts. Justice Stevens wrote a separate opinion concurring with the majority.

The Medellin Case involved José Medellin, a Mexican citizen who had lived in Texas since childhood and was convicted in 1993 of the brutal murders of two teenage girls and sentenced to death.
Medellin signed a confession, having been read his Miranda rights. However, Medellin was not informed of his rights as a Mexican national under the Vienna Convention to notify Mexican consular officials of his arrest and detention.
In 2005 President George W. Bush ordered the Texas judicial system to comply with a 2004 World Court (the International Court of Justice) decision that would have reopened Medellin’s case.
Justice Roberts, writing for the majority, acknowledged that President Bush’s motivations (to insure reciprocal observance by foreign governments of the Vienna Convention and to protect international relations) were “plainly compelling,” but concluded by saying that, “Such considerations … do not allow us to set aside first principles.” In this case, the “first principles” involved the president’s ability to issue a directive that “reaches deep into the heart of the state’s police powers and compels state courts to reopen final criminal judgments and set aside neutrally applicable state laws.”
The Roberts majority rightly decided that treaty obligations do NOT trump American law. Treaty obligations only trump American law when the Congress of the United States acts legislatively to incorporate them into American jurisprudence through legislative action, thus making the treaty obligations part of American law. As Justice Roberts pointedly concluded, “The primary role in deciding when and how international agreements will be enforced” must be left to the legislative branch of the U.S. government, the American people’s elected representatives.
This Supreme Court-erected “firewall” between international law and American domestic law and sovereignty was much needed and will be the enduring legacy of the Medellin decision.