From ABC News:
United States District Judge Henry E. Hudson is expected to issue a ruling targeting a provision of the act that requires individuals to either obtain a minimum level of health insurance coverage, or pay a penalty for failing to do so. The provision is set to go into effect in 2014.
Virginia is challenging the law, arguing that Congress exceeded its authority in passing the legislation and that the law conflicts with a state law already on the books that says residents cannot be forced to buy health insurance.
The Obama administration contends that Congress was well within its authority, under the Commerce Clause, to pass the so called "individual mandate" because the costs of the uninsured translate to interstate economic activity. In court briefs government lawyers argue that in 2009 alone 45 million people—an estimated 15% of the population—went without health insurance.