"My son has not been sober for this length of time since he was 13 years old," Douglas, 65, tells the Today show, in an interview airing Monday. "So he was going to be dead or somebody was gonna kill him, and I think he has a chance to start a new life and he knows that. And from my understanding, it's going to take that amount of time for him to rebuild and start himself afresh."
Cameron Douglas, 31, was arrested last year for allegedly dealing methamphetamine. Last month, he was sentenced to jail time for conspiring to sell crystal meth and for heroin possession.
"He's a great young man," the elder Douglas adds. "And I wouldn't be supporting him if I didn't feel that way."
The Oscar winner (who is revising his famous role of Gordon Gekko in the upcoming Wall Street: Money Never Sleeps).also admits he has grappled with his own sense of responsibility.
"I've taken blame about being a bad father – if being a bad father is working your butt off trying to create a career at one time," he says. "When I had Cameron I was early in my career and as opposed to most jobs, making movies takes you all around the world, so you were absentee in that sense."
But these days Douglas – who has two children, Dylan, 9, and Carys, 7, with his current wife, Catherine Zeta-Jones – says his family life is much more settled. "My priorities have completely changed," says the actor. "My marriage and my families come certainly before my career."
Meet Sandra Bullock's baby! For the whole story – including photos of her son Louis, an emotional interview about her breakup with Jesse James and her life as a new mom – pick up the new issue of PEOPLE, on newsstands now. Click here to save $1 on the issue