The Atlantic Magazine called Leiderman the "Hacktivist's Advocate"[4] for his work defending hacker-activists accused of computer crimes, or so-called "Hacktivism"[5] especially people associated with Anonymous.

[2]Other noteworthy cases Leiderman defended include People v. Diaz, which went to the California Supreme Court and made law on the ability of police to search a cell phone,[15] Louis Gonzalez, who was falsely accused of rape, attempted murder and torture by the mother of his child[16] and was jailed for 83 days before he was released and ultimately found factually innocent,[17] the Andrew Luster or so-called Max Factor heir habeas corpus proceeding, wherein his sentence was reduced by 74 years[18][19] the first-ever trial of medical marijuana defendants in San Luis Obispo County, California County,[20] and Leiderman represented the lead defendant in Ventura County, California's first concentrated Mexican Mafia prosecution.

[22][23] Leiderman was the lead trial attorney for Jonathan Koppenhaver, also known as War Machine, who was convicted of savagely beating and raping his girlfriend, porn star Christy Mack.

"[2] "Leiderman's years at the VCPDO coincided with the passage of California's medical marijuana statute, and the young lawyer started taking possession for sales and illegal cultivation cases.

In addition to defending clients from marijuana-related criminal charges, Leiderman also advises medical marijuana collectives, teaching them the law, writing up their contracts and articles of association, and waiting on retainer for run-ins with the police.

[2] Leiderman is also a founding member of the Whistleblower's Defense League,[27] "formed to combat what they describe as the FBI and Justice Department's use of harassment and over-prosecution to chill and silence those who engage in journalism, Internet activism or dissent.