The Justice Department has rejected New York County District Attorney Cy Vance Jr.'s attempt to have former Trump campaign chairman Paul Manafort transferred to the notorious Rikers Island prison complex ahead of his pending state court trial, amid questions as to why the move was even contemplated in the first place, Fox News is told.

Fox News first reported earlier this month that a New York State judge ordered the transfer at Vance's request. However, because Manafort has been convicted on federal charges, any attempt to move him out of federal custody must be approved by Deputy Attorney General Jeffrey Rosen. On Monday, Rosen denied the attempt, effectively keeping Manafort in federal custody.

“There’s no reason for [Manafort] to go to Rikers," a source close to the case told Fox News. "He can go to his New York initial appearance and then return to federal custody.”

Vance, a Democrat, said in March that a New York grand jury charged Manafort, 70, with 16 counts including residential mortgage fraud, falsifying business records and other charges. He said at the time that “no one is beyond the law in New York.”

Rikers Island is the famous jail in the shadow of LaGuardia Airport. It has been the temporary home of some of the most high-profile violent criminals in the city, including David Berkowitz, the Son of Sam; and Mark David Chapman, the man who killed John Lennon.

LEGAL EXPERTS STUNNED BY 'BARBARIC' ATTEMPT TO SEND MANAFORT TO RIKERS

Vance's effort to have Manafort sent to Rikers attracted immediate criticism from all angles, including prominent progressives.

"Rikers Island & Solitary Confinement are both tortures *no one* should be subjected to," Scott Hechinger, a public defender in Brooklyn, tweeted. "By supporting solitary for Manafort, we support an immoral, barbaric, cruel & unusual practice. Torture w/ long lasting, debilitating mental health consequences. And solitary for one means solitary is available for all."

"It is yet another example of the weaponization of the criminal process for partisan advantage," defense attorney Alan Dershowitz wrote in an opinion piece for Fox News. The Harvard Law professor emeritus suggested that Manhattan prosecutors may have been putting Manafort through tough conditions intentionally in order to prod him to work with them as state officials investigate President Trump.

And, responding to reports that Manafort would be held in solitary at Rikers, Rep. Alexandria Ocasio-Cortez, D-N.Y., likened the move to "torture."

For now, Manafort is expected to await his state trial in a federal prison in either New York or Pennsylvania.

Manafort’s conviction in August made him the first campaign associate of President Trump found guilty by a jury as part of Special Counsel Robert Mueller’s probe. U.S. District Judge T.S. Ellis emphasized ahead of sentencing that the Manafort case was not about Russian interference in the 2016 election.

Ellis said that the guidelines of sentencing Manafort to between 19 and 24 years in prison were "excessive for this case."

Prosecutors said Manafort hid income earned from political work overseas from the IRS while fraudulently obtaining millions in bank loans. Manafort had pleaded not guilty to all 18 counts in the case.

In connection with a separate case in Washington related to foreign lobbying and witness tampering, Manafort ultimately was sentenced to nearly seven years in prison.

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Separately on Monday, the Supreme Court upheld a constitutional rule that allows state and federal governments to prosecute someone for the same crime, a closely watched case because of its potential implications for people prosecuted in the Russia investigation, including Manafort.

The court's 7-2 decision Monday preserves a long-standing rule that provides an exception to the Constitution's ban on trying someone twice for the same offense. Ruling for the defendant in this case might have made it harder for states to pursue criminal charges against defendants in the Russia investigation in the event Trump pardons them.

Fox News' Ronn Blitzer, Edmund DeMarche and The Associated Press contributed to this report.