Former Enron Chief Executive Jeffrey Skilling was unsuccessful in his latest bid to overturn his criminal conviction as a U.S. appeals court called any errors in his trial “harmless.”

A jury convicted Skilling in 2006 on 19 counts, including conspiracy and securities fraud, in connection with the collapse of the one-time energy trading giant. Prosecutors said Skilling’s fraud was an elaborate ruse to fool investors into believing the shaky company was healthy.

He was sentenced to 292 months in prison. However, the U.S. Supreme Court later invalidated one theory underpinning the conspiracy conviction, and instructed the appeals court to review the case again.

The U.S. 5th Circuit Court of Appeals Wednesday found that any error committed by the trial judge was “harmless.” Skilling’s challenge to all of his convictions must fail, the appeals court ruled.

Dan Petrocelli, who represents Skilling, said they believe the court’s decision does not conform to the law.

“We will continue to fight to overturn the wrongful convictions of Mr. Skilling,” Petrocelli said in a statement.

Representatives for the U.S. Department of Justice did not immediately respond to a request for comment.

In Skilling’s case the Supreme Court reduced the scope of the so-called honest services fraud statute, ruling that it only covered bribery or kickbacks. Skilling took neither, so the high court sent the case back to the 5th Circuit to evaluate whether the theory so tainted his case that all or part of it must be tossed.

Since the jury was presented with “overwhelming evidence” that Skilling conspired to commit conspiracy fraud, the verdict would have been the same even if the honest services theory had never been presented, the three judge 5th circuit panel ruled.

The case in the 5th Circuit is United States of America v. Jeffrey K. Skilling, 06-20885.