There is a legal way to do it with 4 wires, plus the grounding conductor. Picture the receptacle in the garage. It takes two wires to energize it, the hot (1) and the neutral (2). Run them from the house. Picture two three-way switches, one at the garage and one in the house. Connect a hot jumper conductor to the top of each three-way. Connect one wire between the pivot-points (or commons) of the two switches (3). The last wire is the switched leg (4). Connect the switched leg to the bottom part of each three-way and to the lights at the garage and the house. Draw it out, it works, and it is legal. (Paralleling the hots with two #12s connected to a 20 amp breaker is legal.) What is not legal is the California hook-up where the ground is used as the return path (neutral), but the rest is the same.