In an age of multilateral agreements to exchange information and other agreements to cooperate in the collection of taxes of another country, many people are unaware of the “revenue rule.” This common law doctrine allows courts to decline entertaining suits to collect tax or enforce foreign tax judgments. In their article, Sunita Doobay of Blaney McMurtry L.L.P., Toronto, and Stanley C. Ruchelman explore (i) the general development of the revenue rule, (ii) its extension to North America, (iii) the applicable provisions of the Canada-U.S. Income Tax Treaty allowing for assistance in the collection of tax and exchange of information, (iv) one U.S. wire fraud case involving evasion of foreign import duties, and (v) several recent cases in the U.S. where taxpayers raised creative arguments to attack the validity of treaty provisions, but to no avail.