I'm new to hunting in Alabama and on Monday I came across some "wildlife openings". What are the rules for hunting over these? I can't seem to find anything in the regs.

Hunt it as long as there is no sign saying not to

And its first come first serve. but be warned i have set up on one and have someone park right beside me and come climb a tree on the other side of gf.

Is this a serious question?

As far as I know there are no special rules specific to greenfields on WMA's in Alabama. I recommend. Not hunting right on one though. My luck hunting greenfields on WMA's increased significantly when I started walking the trails out of the fields back to the nearby thickets and then hunting near the thicket, between it and the field.
Two cents. Its only worth two cents though.

Thanks for the helpful comments.

I second the not hunting on a green field. Your best bet is sitting in a transistion area between the pines and a food source. I've just about made my mind up hunting wmas for the past 6 years the deer don't move out in the open during daylight