I don't see why building a robot in a science room would violate any laws. Perhaps your principal does not understand what you are doing. Maybe he/she thinks that you are welding and doing all sorts of crazy high tech sci-fi stuff.
Sawing, drilling, and assembling is definitely not more dangerous than mixing toxic chemicals together in beakers with the possibility of explosion. A chemistry teacher will argue that he is in control of what gets mixed and so he can prevent any explosions. A robotics teacher can argue the same with regard to building a robot.
I think you and your principal should take a close look at the law in question. If it forbids robot-building, perhaps it forbids chemistry experiements, too. If so, you should ask your principal to make all chem classes drive a few miles down the road to join you in your garage.
