John Prebble (Victoria University of Wellington, Faculty of Law) & Chye-Ching Huang (University of Auckland, Business School) have published The Fabricated Unwind Doctrine: The True Meaning of Penn v. Robertson, 7 Hastings Bus. L.J. 117 (2011). Here is part of the Introduction:

Also referred to as the “rescission doctrine,” a tax “do-over,” or a “tax mulligan,” the effect of the unwind doctrine is that if you change your mind about a transaction, you can avoid its income tax consequences by returning to the economic status quo ante, so long as you do so by the end of the tax year. … Taxpayers routinely rely on the unwind doctrine found in Rev. Rul. 80-581 when they discover that their transactions have unwanted tax consequences. Nowadays, “unwinding” has become a “common if not ubiquitous feature of tax practice.” This article finds that the unwind doctrine has no firm basis in case law. Instead, the unwind doctrine is an IRS fabrication based on the IRS’ misinterpretation of the case Penn v. Robertson [115 F.2d 167 (4th Cir. 1940)].