Extant research has shown that ordinary causal judgements are sensitive to normative factors. For instance, agents who violate a norm are standardly deemed more causal than norm-conforming agents in identical situations. In this paper, we present novel findings that go against predictions made by several competing accounts that aim to explain this so-called "Norm Effect". By aid of a series of five preregistered experiments (N = 2'688), we show that participants deem agents who violate nonpertinent or silly norms - norms that do not relate to the outcome at hand, or for which there is little independent justification - as more causal. Furthermore, this curious effect cannot be explained by aid of potential mediators such as foreknowledge, desire or foreseeability of harm. The "Silly Norm Effect", we argue, spells trouble for several views of folk causality in the literature, and lends support to a Bias View, according to which Norm Effects are the result of blame-driven bias. We close with a discussion of the relevance of these findings for the just assessment of causation in the law.