The US Supreme Court has rejected an appeal that could have overturned death sentences against 51 Mexicans.
Medellin's case has implications for other Mexicans on death row
Jose Medellin claimed his rights had been violated when he was convicted in Texas on rape and murder charges without being allowed consular access.
The International Court of Justice ruled last year that his conviction - and those of 50 other Mexicans - had violated the 1963 Vienna Convention.
But the justices ruled there was no need for intervention at this stage.
They said the case of Jose Medellin would have to run its full course through the Texas courts before they would consider any appeal.
The judges referred to a recent order by President George W Bush instructing individual states to comply with the ICJ ruling and hold new hearings for the convicted Mexicans.
"In light of the possibility that the Texas courts will provide Medellin with the review he seeks, we think it would be unwise to reach and resolve the multiple hindrances to dispositive answers to the questions here presented," the ruling said.
Medellin was one of five gang members sentenced to death in 1994 for raping and murdering two teenage girls.
Last year, the ICJ in The Hague ruled that his and a number of other convictions violated the Vienna convention, which was ratified by the US Senate.
Part of the protocol requires the ICJ to make the final decision when citizens of its signatory nations have been jailed abroad, specifically if they have been denied access to a diplomat from their own country.
The US recently withdrew from that section of the treaty, thereby ensuring the ICJ would no longer have powers of enforcement.
The US state department said it was not appropriate that an international court should reverse the decisions of a country's criminal justice system.