COLUMBUS — President Barack Obama is expected to sign sweeping changes in the American health-care system on Tuesday, but a group of Ohioans Monday began the process of limiting its impact in this state. In a modern-day equivalent of declaring states' rights, the Ohio Liberty Council and the conservative Tea Party movement have launched an effort to amend the Ohio Constitution to declare that no law can force and individual, employer, or health-care provider in the state to participate in the national reforms. It would also prohibit anyone who refuses to participate, including those required to buy or provide insurance,...