Taxpayer use of offensive nonmutual collateral estoppel.

Collateral estoppel should apply to the IRS commissioner if the factual issues at hand have been addressed by a court, even in cases where the taxpayer was not a party to the previous litigation. Cases involving legal, rather than factual, issues could still involve collateral estoppel applied to the commissioner if such a move can be made without violating US v. Mendoza. The commissioner should not be allowed to invoke collateral estoppel against taxpayers who were not parties in the relevant litigation.