Publisher Steven Brill, who is in talks to hire Mitnick as a columnist for his Contentville Web site, has retained New York attorney Floyd Abrams in an effort to lift the restriction, which was ordered last month.
Mitnick said his own attorney, Sherman Ellison, is preparing to challenge the ban on First Amendment grounds. Abrams will submit a so-called friend of the court brief in support of the motion, which is expected to be filed in the next few weeks.
While courts have broad discretion to set conditions for an inmate's release from prison, including limiting the right to freedom of association, Mitnick and his attorneys believe the gag order goes too far.
"This case will ask, 'When does the First Amendment trump the authority of the probation office?'" Mitnick said in an interview.
Mitnick was released from prison in January, after serving nearly five years for breaking into computer systems at companies such as Motorola, Novell, Nokia and Sun Microsystems. The companies said they suffered millions of dollars in damages, a claim Mitnick denies.
In a plea deal, Mitnick agreed for three years to stay away from computers, cellular telephones, televisions or any equipment that can be used for Internet access. U.S. District Judge Mariana Pfaelzer, who approved the deal, said at the time that she expected the terms would limit Mitnick to minimum-wage jobs.
Instead, Mitnick quickly found himself in high demand on the lecture circuit. Since leaving prison, he has testified before Congress on computer security issues, made appearances on TV and radio talk shows, and lined up writing deals.
Mitnick said his probation officer at first encouraged him to pursue writing and speaking jobs. Last month, probation officials decided that such appearances violate the terms of his supervised release and ordered him to stop.
Probation officials could not immediately be reached for comment.