 A further complication was the various shifts in network and affiliate ownership at UPN.Shortly before its launch, Paramount Pictures' corporate parent Paramount Communications was purchased by Viacom, which later purchased a 50% stake in UPN in December 1996, and acquired CBS in 2000.Viacom was permitted to keep interests in both networks, in effect, resulting in the Federal Communications Commission (FCC) lifting its long-standing ban on television station duopolies.