In the first legal attack on the international conspiracy indictment he is facing, Joaquín Guzmán Loera, the accused Mexican drug lord known as El Chapo, filed court papers on Thursday claiming that the Mexican government improperly extradited him to Brooklyn, where he is scheduled to stand trial next year on charges of being the biggest narcotics trafficker in the world.

The papers filed in Federal District Court in Brooklyn were largely a procedural gambit and did not question the heart of the case against Mr. Guzmán, whom prosecutors have accused of killing thousands of people while running the Sinaloa drug cartel and shipping, over decades, at least 200 tons of cocaine into the United States in an ever-changing fleet of trucks, planes, yachts, container ships and submersibles. Instead, the papers focused on the process by which Mexico arranged for Mr. Guzmán’s prosecution in Brooklyn, where he arrived in January under heavily armed guard after being flown from his homeland in a small police jet.

According to Mr. Guzmán’s lawyers, the public defenders Michelle Gelernt and Michael Schneider, Mexican officials initially agreed to extradite Mr. Guzmán to face charges only in Texas or California, two of the seven federal districts where had been indicted in absentia. But on Jan. 19, the day he was placed on the police jet, Mexico suddenly consented to send him to New York, the lawyers said, issuing a waiver to what is known as the Rule of Specialty, which requires defendants to be tried only on the specific charges for which they are extradited.

Ms. Gelernt and Mr. Schneider questioned in their papers how it was feasible for Mexican officials to have followed proper protocols and obtained the waiver within hours of Mr. Guzmán being flown out of Mexico. They also questioned whether Brooklyn prosecutors should be allowed to proceed with attempts to seize from him $14 billion in alleged drug profits when, as they claim, these forfeiture allegations were not included in the original extradition papers.