We have reached the last day of oral arguments for the Patient Protection and Affordable Care Act (PPACA), a.k.a., Obamacare. Two issues remain before the U.S. Supreme Court.

First, is PPACA severable — that is, if one part of the law is unconstitutional, may the rest of the law remain, or must the entire law be thrown out? Readers can find extended coverage on the severability issue elsewhere.

Second, is PPACA's Medicaid expansion constitutionally permissible? Congress' broadening of Medicaid's eligibility rules affects not only the federal budget but the budgets of the states, which, along with the federal government, fund state-managed Medicaid programs. By expanding the pool of who can receive Medicaid, Congress is raising the states' costs; the states' contributions to the program would have to increase to pay for the greater number of beneficiaries. That is bad news for already tight state budgets. Medicaid is a "voluntary" program technically, but practically, states have come to rely heavily on the federal dollars associated with the program. Foregoing PPACA's Medicaid expansion provisions also probably means foregoing those federal dollars.

Therein lies the issue: Do PPACA's revisions to Medicaid, which expand the program's eligibility requirements, constitute permissible federal pressure on the states stemming from Congress' spending power, or does it go beyond "pressure," constituting "compulsion" in violation of the 10th Amendment? For those following the arguments at home, listen for whether and how the justices use the word "compulsion" during the hearing. If the Court believes the changes to the law are "compulsion," it may be inclined to say the Medicaid expansion goes too far, violating the 10th Amendment.

The Court is expected to rule on this week's oral arguments in June or July.