Inverse Reinforcement Learning (IRL) is the problem of finding a reward function which describes observed/known expert behavior. IRL is useful for automated control in situations where the reward function is difficult to specify manually, which impedes reinforcement learning. We provide a new IRL algorithm for the continuous state space setting with unknown transition dynamics by modeling the system using a basis of orthonormal functions. We provide a proof of correctness and formal guarantees on the sample and time complexity of our algorithm.