Steering Column not locking

What is your question?

My mother purchased a 2004 Buick Park Ave. Here is what is happening. If the Tilt steering is all the way up, key is out, you cannot move the column shifter. I figure this is normal for locking the steering. NOW if I drop the Tilt steering down, with the key not in, I am able move the Column shift to neutral or where ever I want and the car will start rolling down or up hill if the emergency brake is on. Is there some type of sensor that controls this?