Former Qwest CEO Joe Nacchio, having recently completed a prison sentence for insider trading, maintains that he never committed any crime and that the sole reason for his conviction can be summed up in three letters: NSA.

In an interview with the Wall Street Journal, Nacchio said former security contractor Edward Snowden's revelations about far-reaching domestic spying programs conducted by the US National Security Agency backed up his claim of innocence, which has never wavered since his 2007 trial.

"I feel vindicated," Nacchio told the paper. "I never broke the law, and I never will."

During his trial, prosecutors argued that Nacchio sold $52m of Qwest stock because he knew the telco's fortunes were tanking. He says that's not true – that when he sold the shares he thought Qwest's outlook was good.

What he did do, he says, is turn down the NSA's 2001 request that he give the spy agency access to Qwest customers' phone records. Qwest was the only US telco to do so at the time, he claims, and his prosecution for securities fraud was a government reprisal.

Nacchio says he had planned to submit records of Qwest's dealings with the NSA as part of his defense, but that some of the materials he wanted to include were deemed classified and he was barred from presenting them as evidence.

As a result of his conviction, Nacchio paid a $19m fine, forfeited another $44.6m, and was handed a six-year prison sentence, which he served in minimum-security facilities in Pennsylvania. He was released on September 20 after serving 54 months.

Having entered prison looking every bit the plump-faced, well-heeled corporate exec, the 64-year-old Nacchio's body has been hardened by weightlifting and he now sports a shaved head and goatee reminiscent of Breaking Bad's Walter White.

Six years after his conviction, he's still in and out of the courts. He has sued his criminal defense lawyers for overbilling and malpractice (the latter claim since having been dismissed), and he's reportedly seeking an $18m refund from the Internal Revenue Service, based on his claim that the funds he was made to forfeit should have been tax deductible.

He's also looking for a book deal. He has two in mind: the first about Americans' loss of liberty from the actions of the NSA and other government agencies, and the second a memoir of his own experiences in federal prison. Nacchio describes his incarceration as being like "Lord of the Flies, for grown-ups," and among his more colorful claims are that his best friends inside were drug offenders who went by "Juice" and "Spoonie," and that his bunkmate was called "Spider."

"I trust Spoonie and Juice with my back," Nacchio told the WSJ. "I wouldn't trust the guys who worked for me at Qwest." ®