Fan favourite Vaughan, 33, checked in last week to return to the club he left 10 years earlier, as Cowan’s first new signing of the summer.
The all-action right-back seldom lacked enthusiasm in Bucks white during his first spell at the club, which lasted four years and included promotion to step two and Setanta Shield success.
He picked up six red cards across 179 games, including one at Hyde towards the end of his Bucks stint, shortly before he made the switch to Kidderminster Harriers, then of the division above.
And Vaughan was also dismissed, as well as missing an early spot-kick, against former club Telford at Aggborough in October 2011.
But boss Cowan says his new recruit, who he believes Telford ‘had no right’ to sign, has an ‘immaculate’ disciplinary record in recent years.
Cowan said: “I suppose his discipline was probably an issue when he was younger but as he’s got older it’s been immaculate. That comes with age and experience.
“He’s a guy with a huge heart, a very exciting player and is very team dependable as well. We’ll be able to depend on him. It’s a real coup. Since me and Lee played together we’ve been good friends and kept in touch very regularly.
“Really I don’t feel like we had any right to sign him, is the truth – he’s had offers from the league he was playing in and he’s made the decision, although he’s still very ambitious football-wise and wants to be successful, he recognises he’s delaying the inevitable and wanted to look at the transition to part-time.
“We’ve reaped the benefits of that. Ordinarily I don’t think we had any right to sign anybody of his quality and calibre.
“But it just fitted right. I was able to tell him this is the place he needed to be and he’s convinced and over the moon and excited on what’s to come.”
Vaughan progressed to the Football League with Cheltenham and has since represented Tranmere, before another spell at Harriers and most recently Solihull Moors.
He rebuffed offers from National League clubs to return to Shropshire, which marks a switch to semi-professional football.
And Cowan stressed rumours that he joined Telford for ‘big money’ were untrue and an ‘injustice’.
“I’ve heard a few people say we must be paying him big money, that does Lee an injustice, he’s certainly not come for the money,” the boss added. “He’s been offered some very, very good deals and I think it does him an injustice to say we’re paying him big money. The reality is we’re just not. He’s come because he really believes with what we’re doing and it fits well with his goals. He could’ve gone to other clubs part-time for more money.
“He loved his time here last time and believes and trusts me and I could get him over the line. If it was a money decision he certainly wouldn’t be signing for us.”