God as an authoritative figure

Someone comes and asks you, “I believe in God, but why obey His commandments and laws?!” You answer, “If you ask, it means you don’t understand what it means to believe. Believing in God means believing in a being who has the authority to make things obeyed.” A difficult question indeed.
However, perhaps we can advise you like this:
God has the authority to define situations in which I must sit in the Sukkah, but it still imposes on me a duty of behavior. In other words, the deontic term “must” can be interpreted in two ways: either as a definitional rule (which defines states of affairs in the world) or as a behavior rule (which imposes on the recipient a duty to do something).
For example, a minor may be “owed money” (if he stole or borrowed, for example), but this obligation does not impose any duty of conduct on him (to the best of my knowledge).
 
So the same can be said about God. Although he has the authority to define situations, how does he have the authority to impose a duty of behavior on me?