CBS acquired what was formerly Paramount Television in the split from Viacom. That gave them the licensing rights to a ton of TV shows, including every Trek series. Under the new arrangement, Paramount Pictures (the remaining movie division) continues to make Trek movies
under license from CBS.
Pretty much everything made over the last ten years, but here's the list of properties that can be licensed from CBS Consumer Products itself (look at the "Star Trek" tab):
http://www.cbsconsumerproducts.com/properties.html
Paramount these days is a renter of Trek's IP, not an owner.