Automatic lockers are normally locked, even in 2wd. They unlock to allow the outside tire in a turn to rotate faster through the turn, then lock back up again once you're driving straight again.
That said, in a TJ, there is no torque being passed into the front axle via the driveshaft so any front locker present is not locked up "hard" in 2wd. It is locked, to be sure, but with no torque being sent through it when you're in 2wd, it unlocks so easily for turns that you can't even tell a front locker is there when you're in 2wd.
It's when you shift into 4Hi or 4Lo that the transfer case finally sends power (torque) via the front driveshaft through a locker which then causes it to lock up hard enough that you'd notice it. On a paved road, it'd cause problems in 4Hi or 4Lo but offroad, it's fine.
So with a front locker, it only cause problems on paved roads when you're in 4x4. In 2wd, you can't even really tell it's there. I have a Powertrax automatic No-Slip locker in my front axle and honestly, I can't tell it's there in 2wd.
The same is not always true for other non-TJ 4x4 vehicles where many always send power to the front axle, 4x4 or 2wd.