MEXICO CITY, Mexico (CNN) -- The United States violated international law by putting a Mexican national to death in Texas, the Mexican government said Wednesday.
Protesters gathered before the execution of Jose Medellin in Huntsville, Texas, Tuesday.
Protesters for and against Jose Ernesto Medellin's execution gathered before he was put to death Tuesday night in Huntsville, Texas, for raping and murdering two teens in 1993.
His death ended 15 years of legal disputes on a sour note.
"The government of Mexico sent the U. S. Department of State a diplomatic note of protest for this violation of international law, expressing its concern for the precedent that it may create for the rights of Mexican nationals who may be detained in that country," the Mexican government said in a written statement.
"The Ministry of Foreign Relations reiterates that the importance of this case fundamentally stems from the respect to the right to consular access and protection provided by consulates of every state to each of its nationals abroad."
Medellin's execution was also the first of what promises to be a busy month at the state's death chamber in Huntsville. Five other men are scheduled to die in the next four weeks by lethal injection, including Honduran native Heliberto Chi Acheituno on Thursday.
Mexico took the case of Medellin and four other Mexican nationals on death row to the International Court of Justice at The Hague. The court ruled in 2004 that the United States had violated the Vienna Conventions of Consular Relations, which requires a country to notify another country when one of its nationals is accused of a serious crime.
Under the Vienna Conventions, arrested suspects are also eligible for legal assistance from their consulates.
After the ICJ ruling, President Bush reluctantly ordered Texas to comply with that decision and reopen Medellin's case. Texas appealed. In March the U.S. Supreme Court ruled the Vienna Conventions were not binding on the United States, which is a signatory to them, because Congress had not passed a law requiring their enforcement.
The president cannot establish binding rules "that pre-empt contrary state law," Chief Justice John Roberts wrote in the majority opinion.
The ICJ ruled again last month that the executions should not be carried out pending a ruling on a request for further interpretation of the 2004 ruling. But Texas, which had set Medellin's execution date immediately after the Supreme Court ruling, carried out the execution Tuesday night after the Supreme Court denied an appeal for a stay.
In June, Secretary of State Condoleezza Rice and Attorney General Michael Mukasey asked Texas Gov. Rick Perry to delay the execution.
"We continue to seek a practical and timely way to carry out our nation's international legal obligation," wrote the Cabinet officers, "a goal that the United States needs the assistance of Texas to achieve."
U.N. Secretary General Ban Ki-Moon also asked Texas officials this week to delay the capital punishment.
Medellin's lawyers, who argued that Mexican consular officials were not able to meet with the man until after his conviction, condemned the execution.
"With this action, our nation has broken a commitment willingly made by our president and our Senate," the lawyers said in a written statement. "We must now hope that other nations stand stronger in their promises than we do, lest our own citizens be placed at risk elsewhere."
Journalists who witnessed the execution said Medellin apologized to his victims' families before he received the lethal cocktail.
Medellin was 18 when he participated in the June 1993 gang rape and murder of two Harris County girls, Jennifer Ertman, 14, and Elizabeth Pena, 16.
CNN's Bill Mears contributed to this report.