Joaquin "El Chapo" Guzman asked a federal judge in Brooklyn to suppress statements prosecutors claim the drug kingpin made during his January 2017 extradition to the United States.
In a court filing Thursday, his defense attorneys said that it is not clear whether Guzman had been informed of his rights.
Guzman was flown from Mexico to the United States on Jan. 19, 2017, to face what Balarezo called "a laundry list of offenses," including operating a continuing criminal enterprise, participating in a wide-ranging drug trafficking conspiracy and distributing cocaine.
Balarezo did not mention the substance of the statements made by Guzman during the flight, but he said he was made aware of them earlier this month when the government disclosed their existence in a sealed filing.
"The government has not disclosed any information that indicates that the agents advised Mr. Guzman of his rights or that he waived them," Balarezo said.
Judge Brian Cogan, who is overseeing the case against Guzman, did not immediately rule on the defense request.
Guzman faces up to life in prison if convicted but has pleaded not guilty.
His trial is set for September.
Cogan has said he plans to summon as many as 1,000 potential jurors who would arrive as soon as next month to receive questionnaires.