Several scholars have documented the positive consequences of job-hopping by inventors, including knowledge spillovers and agglomeration and the concentration of spinoffs. This work investigates a possible antecedent of inventor mobility: regional variation in the enforcement of postemployment noncompete covenants. While previous research on non-competes has been largely focused on California and Silicon Valley, we exploit Michigan's inadvertent reversal of its noncompete enforcement legislation as a natural experiment to investigate the impact of noncompetes on mobility. Using the U.S. patent database and a differences-in-differences approach between inventors in states that did not enforce and did not change enforcement of non-compete laws, we find that relative mobility decreased by 34% in Michigan after the state reversed its policies. Moreover, this effect was amplified 14% for "star" inventors and 17% for "specialist" inventors.