You will not be able to target him with spells or abilities that require a target because of the smoke. However you can hit him with projectile spells/abilities if you shoot them in his direction.
I am well aware of the fact that you can aim past a hidden/invisible enemy and have the projectile hit them on the way through, but I am referring to instances where such a spell allows me to target them, I have alternated between multiple spells (without actually casting them, just selecting each in turn and trying to target the enemy to see what the game tells me) and the teleport spell was the only one saying that the enemy was hidden and couldn't be targeted.