However, it turns out that Mexico is upset and has complained that its citizens were not given access to a Mexican consulate. What that consulate planned to do is not really clear as there is absolutely no question of the men's guilt — they've admitted to the crime. Oh, and apparently Jose Medellin never actually asked to speak to the consulate, and Texas didn't know for a while that the men were Mexican nationals.
But this is an international case, and the ICC has interfered several times, forcing the issue to the Supreme Court a few times as well.
The treaty in question is the Vienna Convention on Consular Relations, which was adopted in 1963. The story is complex, but it boils down to the fact that the federal government, in the person of President Bush, cannot order a state court to do something.
So the World Court ordered the United States on July 16, 2008, to not let Texas execute the first of the criminals involved in this case, though the United States Supreme Court stated that the federal government cannot prevent the executions.
So now the United States is left in a quandary that's unlikely to be resolved. How can it fulfill its treaty obligations when Congress has not given power to enforce the treaty? And Congress, despite the attempts of some Democrats, is not likely to free five murderers on death row.
In any case, the World Court has tried getting involved again, ordering the United States government to force Texas to not execute the clearly guilty men. Texas, on the other hand and not to put too fine a point on it, has told the World Court where to go and what it can do once it gets there. And it fully plans on executing Medellin for his crime.