AP file Dzhokhar Tsarnaev, the surviving suspect in the Boston Marathon bombings, is being held in federal custody while he awaits trial.

Restrictions put on imprisoned Boston Marathon bombing suspect Dzhokhar Tsarnaev are so harsh and isolating that he's having a hard time helping prepare for his defense, his attorneys told a judge on Wednesday.

The attorneys asked the judge to lift the restrictions on Tsarnaev as he awaits trial.

As outrage has spread over the cover of the new issue of Rolling Stone magazine, which features alleged Boston bomber Tamerlan Tsarnaev, the magazine is standing by their decision to feature him. NBC's Kristen Dahlgren reports.

In a 23-page motion filed in U.S. District Court in Boston, attorneys write that so-called "Special Administrative Measures" imposed by the U.S. attorney a month after Tsarnaev's arrest are "extraordinary and severe," and illegal under the circumstances.

The wide variety of restrictions on how and who Tsarnaev can communicate with were put in place, prosecutors said, because of the risk that Tsarnaev's communication might lead to more bloodshed because of his "continuing desire to incite others to engage in violent jihad."

Those restrictions also guide how Tsarnaev is treated in prison.

“The restrictions on Mr. Tsarnaev leave him in nearly total isolation,” the defense attorneys said in the motion. “He is confined to his cell except for legal visits and very limited access to a small outdoor enclosure, on weekdays, weather permitting. The purported basis for these conditions lies in the crimes he is alleged to have committed prior to arrest, not any behavior during his confinement.”

The attorneys argue that the restrictions are “effectively punitive,” violating the due process guarantee of the Constitution.

“The negative effects of isolation on detainees are well-documented. Indeed, the United Nations identifies long-term solitary confinement as a form of torture,” the attorneys wrote.

Dzhokhar was wounded in the manhunt for him after the bombing and spent weeks in a prison hospital.

The 20-year-old Tsarnaev faces federal charges, including using a weapon of mass destruction, bombing a place of public use, carjacking, conspiracy and firearms violations that could bring the death penalty.

The April 15 bombing near the finish line of the Boston Marathon killed three people and wounded 264 others.

His older brother Tamerlan, a suspected accomplice in the bombing, was killed in a firefight with police.