Only when using Hircine's ring or if your a werewolf from the "Circle". It was never controllable to begin with unless using the Ring. Why do you think Sinding wanted the ring so badly? This isn't Underworld. Honestly, werewolves should of been having lunar and forced transformations in the game, but to appeal to the younger casual audiences, they did not.
I rather suspect Bethesda didn't implement forced transformations because of all the extra coding it would involve:
1) Having to account for transformations during scripted events and adjusting accordingly
2) Scripting more appropriate responses during random encounters (so we don't experience absurd situations like thieves trying to rob werewolves).