A few comments off the top of my head.
First, if you have a Class 3B laser, this may very well mandate that you need a variance. And a variance mandates that you do certain things, among them, inform the FAA if you are going to shine a laser into airspace, and get permission before doing so.
While there may not be a law specifically prohibiting the shining of a laser into airspace, I believe legislation was recently passed preventing anyone with any laser (of any power, even Class 2) from shining it into a cockpit, automobile, or otherwise interfering with the safe use of other kind of moving vehicles. This might not be the exact wording, but the bottom line is -- don't shine a laser at pretty much anything except for a projection screen and, perhaps (if you have a variance) on buildings and other termination structures.
Bill