There are many results that show that causality is indeed the fundamental notion of physics. In particular, it is known that for pointwise events, causality implies the Lorentz group. In quantum field theory, it is known that pointwise particles lead to divergences and therefore nonpoint particles are necessary (e.g., strings). Since particles are nonpoint, events occurring to these particles are also nonpoint events. In this paper, we show that even if we consider nonpoint events, causality still implies the Lorentz group. In other words, even for nonpoint events, the notion of causality is still fundamental.