TORONTO - Former Canadian media baron Conrad Black has formally requested a release from jail while his lawyers use a recent U.S. Supreme Court ruling to fight his convictions for fraud and obstruction of justice.

Black's lawyer made the filing Tuesday with the 7th Circuit Court of Appeals in Chicago, now that the top court in the United States sent his 2007 fraud convictions back to a lower court.

The Supreme Court ruled that a law used to help convict Black on three counts of mail fraud had to be applied more narrowly. The ruling didn't exonerate Black but does give him another chance to argue against his convictions.

In addition to fraud, Black was convicted of a more serious count of obstruction of justice that carried a 6 1/2-year sentence, which Black is serving in a Florida jail. The obstruction charge wasn't part of the Supreme Court's decision but Black's lawyers are arguing the obstruction conviction should also be thrown out.

In the request for bail, Black's lawyers say the Supreme Court's "rejection of the fraud theory goes to the heart of the most hotly contested issues at Mr. Black's trial -- whether there was a scheme to defraud and whether Mr. Black 'corruptly' intended to obstruct the investigation of this non-crime..."

On the obstruction conviction, "the government's proof of corrupt intent was desperately threadbare," the application states.

Admitting that it is possible for someone to be convicted of obstruction even if acquitted of the underlying crime, "the question here is whether this jury undoubtedly would have ruled for the government on the crucial, disputed element of 'corrupt' intent if it had been aware that the offence Mr. Black was supposedly endeavouring to obstruct was, as he maintained all along, not a crime at all."

Prosecutors say Black should remain in the low-security federal prison because the ruling doesn't affect the obstruction of justice count.

This isn't the first time that Black has submitted an appeal. In 2008, he pushed ahead with an attempt that was rejected by the appeals court, and later was refused bail while he made further appeals.

In the latest filing, Black's lawyers attempted to establish a difference between the two bail attempts.

"The Supreme Court now unanimously ruled that violation affecting Mr. Black's Sixth Amendment jury trial right."

The Hollinger International media empire, which Black controlled through a series of public and private Canadian companies, once owned the Chicago Sun-Times, The Daily Telegraph of London, The Jerusalem Post and hundreds of community papers in the United States and Canada.