article 53 of the procedures for handling criminal cases by public security organs. if a defense lawyer requests to meet with a criminal suspect in custody, the detention center shall arrange for a lawyer to meet with the criminal suspect within 48 hours after checking the lawyer's practice certificate, law firm certificate, power of attorney or legal aid letter of the criminal suspect, and notify the case handling department at the same time. In the process of investigation, when the defense lawyer meets the criminal suspect who is detained or under residential surveillance in criminal cases endangering national security or terrorist activities, the detention center or the residential surveillance execution organ shall also check the license decision document of the investigation organ.