"The Federal Government does not have the power to order people to buy health insurance. Section 5000A would therefore be unconstitutional if read as a command. The Federal Government does have the power to impose a tax on those without health insurance. Section 5000A is therefore constitutional, because it can reasonably be read as a tax," Roberts said in his opinion
Again, the supreme court is supposed to give great deference to Congress. And Roberts did in this case. He should have done so in the Citizens United case as well.