The future of Obamacare is hanging by a legal thread, thanks to what its supporters have passed off as a mere "drafting error." Now MIT professor Jonathan Gruber, selected by Gov. Shumlin to receive yet another juicy contract to try to make sense out of Green Mountain Care, finds himself uncomfortably in the spotlight of the legal issue.

The Affordable Care Act of 2010 (Obamacare) contemplated the creation of health insurance exchanges in every state. An earlier version in the Senate mandated states to create such exchanges, through which federal tax credit subsidies would flow to persons buying government-approved insurance.

But somebody in the Senate realized that the Federal government cannot just mandate the states to do whatever Congress wants. So the final Senate bill, that became law, offered incentives to the states to create their own exchanges. It also authorized the federal government to create a backup exchange in case states declined to create their own.

The incentive was the availability of billions of subsidy dollars to insurance buyers in "exchanges created by the state under section 1311." However the law did not provide for such subsidies to flow through a backup federal exchange created under section 1321.

To the dismay of the Obamacare backers, only 14 states attempted to set up exchanges. (Vermont Health Connect -- $170 million -- remains an inoperable disaster. )

Undaunted, the Obama IRS simply rewrote the law to allow the subsidies to flow through the federal exchange (