Legal Question in Real Estate Law in California

Of course you can sue it. However, I assume what you really mean to ask is "If I sue my apartment company, am I likely to win?" Without knowing the nature of the "little rule" or your breach of it, I cannot predict the outcome of a lawsuit over it. Many factors including how much you like your place, what it'll cost to move, etc. in addition to the likelihood of winning and the costs of suit if you lose would weigh on the decision. Also, don't overlook the possibility that the apartment management may have additional as-yet unmentioned claims against you.