Should we see major tax reform, taxpayers will clamor for guidance from Treasury and the Internal Revenue Service ('IRS') regarding new provisions, as they did after passage of the Tax Reform Act of 1986 ('1986 Act'). Indeed, the greater the degree of reform, the greater the need for guidance. Treasury and the IRS will feel compelled to issue guidance as quickly as possible. If so, they are unlikely to rely on regulations subject to time and resource consuming notice-and-comment by the public. Instead, they will look to guidance not subject to pre-issuance notice-and-comment - temporary regulations in particular, as was the case after the 1986 Act, along with revenue rulings, revenue procedures, and notices.This administrative response to major tax reform in the 21st century, however, will face hurdles unknown at the time of the 1986 Act, hurdles that could constrain the ability of the IRS and Treasury to issue guidance that courts will uphold. One is heightened interest...