The vast majority of gun-owners depicted in CSI (I don't watch the spin-offs, but follow the main one each week) have actually been lawful folks. Even the amature bomb-building 'nutjob' (and I use the term lovingly) was shown to be operating in a legal way, and was treated like a hero by the cast after he died.
In one episode, when a kid suspected of shooting the bully at school was found with gunshot residue on his hands and sleeves, his excuse of "I was at the range this morning." didn't elicit any shock from the investigating detective and CSI staffer... Just a healthy dose of "Yeah, right..."
Law & Order (although moreso its two spin-offs) is a bit more openly anti-gun, although one could argue that as a show set in New York that tries to be dramatically accurate in representing its characters as "real" NYC detectives and assisstant district attorneys an anti-gun attitude from them is realistic. Jack McCoy has always been written as a liberal, and as anti-gun; the ling-running police characters (Briscoe, Logan, Greene) seem to have the typical cop attitude towards handguns... They're used to kill folk, you owe it illegally, why shouldn't I think you used your illegal gun to illegally kill someone?
I'd say the L&O franchise is moderatly anitgun, but CSI seems to be moderatly pro-self defense. With all of the actors being pretty darn good in their weapons handling, in one episode Catherine Willows (Marg Helgenberger) has to pull her gun on a stalker/rapist at point-blank range and does a beautiful strong-arm push, close-in draw. Looked like she'd spent a good week in a CCW course for that one.