Scholars and other commentators widely assert that enforcement of contractual and other limitations on labor mobility deters innovation. Based on this view, federal and state legislators have taken, and continue to consider, actions to limit the enforcement of covenants not to compete in employment agreements. These actions would discard the centuries-old reasonableness standard that governs the enforcement of these provisions, often termed “noncompetes,” in all but four states (notably, California). We argue that this zero-enforcement position lacks a sound basis in theory or empirics. As a matter of theory, it overlooks the complex effects of contractual limitations on labor mobility in innovation markets. While it is frequently asserted that noncompetes may impede knowledge spillovers that foster innovation, it is frequently overlooked that noncompetes may encourage firms to invest in cultivating intellectual and human capital. As a matter of empirics, we show that two commonly referenced bodies of evidence fail to support zero enforcement. First, we revisit the conventional account of the rise of Silicon Valley and the purported fall of the Boston area as innovation centers, showing that this divergence cannot suitably be explained by differences in state law regarding noncompetes. Second, we show that widely cited empirical studies fail to support a causal relationship between noncompetes, reduced labor mobility, and reduced innovation. Given these theoretical and empirical complexities, we propose an error-cost approach that provides an economic rationale for the common law’s reasonableness approach toward contractual constraints on the circulation of human capital.