In the latest National Review:

The Obama Administration is urging federal judges to save its health-care program from absurdity.  It’s a little late for that. 

The Obamacare law enacted in March 2010 authorizes the federal government to provide tax credits for people who buy health insurance on exchanges established by state governments.  It repeatedly refers to exchanges, “established by the State,” especially when discussing tax credits.  Because opposition to the law has run higher and longer than its supporters ever expected in early 2010, however, most states have not established exchanges.   

The law authorizes the federal government to establish exchanges for states that refrain, but has no provision allowing tax credits to be offered to defray the cost of insurance policies offered on those federal exchanges.  Without the tax credits, though, the policies will be prohibitively expensive for so many people that the law will not work.