The health care case before the Supreme Court is actually three cases – National Federation of Independent Business v. Sebelius, Florida et al. v. Department of Health and Human Services, and Department of Health and Human Services v. Florida et al. The court consolidated the first two and agreed to hear the issue raised in the third, which concerns a 145-year-old law.

The central issues before the court:

· Does Congress have the power to require Americans to buy health insurance? The "individual mandate" is the central issue of the case: opponents assert that Congress does not have the power to compel people to engage in commerce; others argue that Congress acted within its authority under the Constitution's commerce clause. Under the law, people who defy the requirement to acquire health insurance will be subject to federal penalties.

· Can the federal government compel the states to expand Medicaid? The law changes the eligibility rules so millions of people will be added to Medicaid, which is run by the states with federal assistance. Florida and the 25 states that joined its lawsuit say the Medicaid expansion is an unconstitutional coercion of the states by the federal government, because Washington threatens to withhold Medicaid funding from states that don't comply.

· If one part of the law is struck down, does the whole law become invalid? This is the "severability" issue. It is important because some have argued that certain provisions of the law depend on the individual mandate and cannot stand without it. These include "insurance exchanges" where individuals may shop for coverage, and the "guaranteed issue" rule, which holds that insurers may not turn anyone down because of a pre-existing condition.

· Do the lawsuits against the health care act violate the Anti-injunction Act? This 1867 federal law says, in effect, that people may not claim to have been harmed by a tax unless the tax has actually been assessed on them. (The "tax" in this case is the penalty people will be compelled to pay if they fail to get health insurance.) The mandate does not take effect until 2014, so harm to citizens so far is theoretical. In addition, some argue that the penalty is not a tax, so the Anti-injunction Act would not apply.

Sources: U.S. Supreme Court, Kaiser Family Foundation, scotusblog.com, New York Times, Reuters news service.