I'm pretty sure the drip leg is required by code everywhere. Even if it's not specifically required by code, it's still the right way to do it. We have a drip leg on both our furnace and water heater, and another one on the main supply line. The purpose of the drip leg is to catch moisture and debris before it enters the appliance where it can interfere with the operation of gas valves. This can cause the appliance to not operate properly, or even worse, it can cause a gas leak which can result in an explosion. In this case, doing it the right way only requires a couple extra dollars in materials, and only requires a couple extra minutes of your time. Why not do it the right way?