First, try to meet them so you can talk about this. I don't know what your driveway situation is like (shared vs clearly separate) but you should start by giving them the benefit of the doubt and making an effort to make sure they realize that that is your driveway.
If you can't get anywhere by being neighborly, you can call the cops because they're trespassing.
And for god's sake, why do you assume this is drug activity? Plenty of people get up that early for perfectly legitimate reasons. Don't make assumptions about people you don't know.