The Constitution grants to Congress the power to regulate interstate commerce. (Everyone agrees that the health insurance market is interstate commerce, so that's not an issue). ObamaCare is constitutional because the law regulates the health insurance market -- which is interstate commerce.
Everyone also agrees that just about each person in the United States will need to use the health care system at some point in their life. At some point in their life they will be responsible for paying for that care. ObamaCare is constitutional because it regulates the timing of that payment.
Conservatives have claimed ObamaCare is unconstitutional because it requires someone to buy something they don't want to buy. They are saying that Congress is trying to regulate "inactivity" (not buying insurance), which is something that Congress has never been able to do before.
The reason that the Conservative argument won't work is because 99%+ of Americans will eventually have to buy health care. So, Congress is not regulating "inactivity," it is regulating "delayed activity." In other words, the decision not to buy health insurance is, in itself, an economic decision that affects interstate commerce, and, most importantly, that uninsured person will almost certainly have to pay for health care, and somebody is going to have to pay that price. Why shouldn't they pay for it now? In addition, Congress has regulated "inactivity" in the past. A couple examples include the requirement that hotels and restaurants serve minority customers, and a requirement that a parent pay child support. (Arguably, Congress also ordered some farmers to buy wheat as well -- but that's a longer story!).
Conservatives have also claimed that ObamaCare stretches Congressional power too far, making it possible for future congresses to create a law that orders everyone to "buy a health club membership to stay fit" or "buy broccoli to eat healthy." The reason this argument fails is because the health insurance/health care market is truly unique. Also, the Supreme Court has a lot of old cases that prescribe rules to help them decide future cases, and these cases have all required that any law be "rationally related" to the important problem. Laws ordering us to buy broccoli or health club memberships would not be rational.
For some additional background, it is important to know that the Supreme Court has within recent memory only found two of Congress' laws to be unconstitutional based on the Commerce Clause. One of the cases dealt with local gun control laws, and the other dealt with domestic violence laws. The Supreme Court held that these laws were unconstitutional because they really didn't have much to do with interstate commerce. (They were probably right.). There is no question that health care/health insurance does involve interstate commerce.
The ability of Congress to regulate commerce has steadily grown through the courts since at least the 1930s. This is mostly because the nation's economy has grown to be so intertwined. Back in the days of the Founding Fathers, your average American bought almost everything from the local farmer or local market or local blacksmith. Things have changed, and the laws have kept pace.
Finally, the Supreme Court is supposed to respect Congress and the congressional power to write laws. Furthermore, the Supreme Court has to approach the case from the mindset that the law is constitutional.
Those were the main issues discussed yesterday in the Supreme Court. If anyone wants to go into the tax side of the argument, feel free! On one last side note, perhaps the most important piece of evidence for the United States' case was RomneyCare in Massachusetts. I kid you not! RomneyCare shows that the market system that ObamaCare will be can be successful in bringing people into the market and avoiding the financial catastrophes of sudden illnesses or injuries. Because of that, I wanted to thank Governor Mitt Romeny below the fold.
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Thanks for the evidence, Governor! I cannot think of any way you could've been a better "witness" for the defense.