A new memo from the Congressional Research Service explains that the next president cannot simply stop ObamaCare (“PPACA”) by executive order:

[A] president would not appear to be able to issue an executive order halting statutorily required programs or mandatory appropriations for a new grant or other program in PPACA, and there are a variety of different types of these programs. Such an executive order would likely conflict with an explicit congressional mandate and be viewed “incompatible with the express…will of Congress”…However, there may be instances where PPACA leaves discretion to the Secretary to take actions to implement a mandatory program, and…an executive order directing the Secretary to take particular actions may be analyzed as within or beyond the President’s powers to provide for the direction of the executive branch.

In other words, the worst elements of ObamaCare — the government price controls it imposes on health insurance, the individual mandate, and the new spending on health-insurance entitlements — are “statutorily required programs” that, say, President Romney cannot repeal or even halt by executive order.

However, there is one executive order that could effectively block ObamaCare, and that lies well within the president’s powers.

The Obama administration has issued a proposed IRS rule that would offer “premium assistance” (a hybrid of tax credits and outlays) in health insurance “exchanges” created by the federal government. The only problem is, ObamaCare only authorizes these tax credits and outlays in “an Exchange established by the State.” The administration did so because without premium assistance, ObamaCare will collapse, at least in states that do not create their own Exchanges. Yet the executive branch does not have the power to create new tax credits and outlays. Only Congress does. So if the final version of this IRS rule offers premium assistance in federal Exchanges, it will clearly exceed the authority that Congress and the Constitution have delegated to the executive branch.

In that case, the next president could issue an executive order directing the IRS either not to offer premium assistance in federal Exchanges or to rescind this rule and draft a new one that does not. The U.S. Constitution demands that the president “take Care that the Laws be faithfully executed.” Such an executive order therefore lies clearly within the president’s constitutional powers: it would ensure the faithful execution of the laws by preventing the executive from usurping Congress’ legislative powers.

While such an executive order would not repeal ObamaCare, as Jonathan Adler and I explain in this Wall Street Journal oped, it would “block much of ObamaCare’s spending and practically force Congress to reopen the law.”