In the mid-1990s, many states as well as the federal government began to regulate early postpartum hospital discharge. Length-of-stay patterns changed markedly in response, but effects were much greater in some states than others. In particular, laws directly empowering patients appeared more effective than laws requiring providers to follow practice guidelines. In addition, the effectiveness of regulation could potentially be influenced by state environment, such as managed care penetration as well as exposure to media attention and public pressure on the issue, though these factors alone were insufficient to cause general behavior change. Furthermore, the 1996 federal law had little effect beyond state laws, suggesting that it did not provide substantial benefits to women in self-insured plans exempted from state law regulation by the Employee Retirement Income Security Act. Findings from this study could provide lessons for similar patient protection initiatives.