When President Obama's health care overhaul became law two years ago, California lawmakers jumped into action. Within months, they adopted several state laws that implement or build on the federal measure, including one to create a state health insurance exchange and another to allow young adults up to age 26 to remain covered by their parents' health insurance policies. Lawmakers passed even more bills related to the overhaul last year and continue to debate sweeping proposals now. The difference this year is that the fate of those state laws, and the impact they will have on Californians, hang under what state Sen. Ed Hernandez calls a "cloud of uncertainty." Before the end of the month, the U.S. Supreme Court is expected to rule on the constitutionality of the Affordable Care Act. Among the most likely scenarios, the court may leave the federal health law intact, overturn it completely or strike down a key provision that requires most people to purchase health insurance. Each possibility carries different implications for California, a state that took an early and aggressive approach to implementing the federal law. "We will have to rethink everything" if the federal law is overturned in part or whole, said Hernandez, D-West Covina, chairman of the Senate Health Committee. "We have to reassess all of these measures. Some of them are actually contingent upon the implementation of the Affordable Care Act."