Articles XIX and XXI of the 1942 Convention Respecting Double Taxation (1942 Convention) between the United States and Canada require the United States, upon request and consistent with United States revenue laws, to obtain and convey information to Canadian authorities to assist them in determining a Canadian taxpayers income tax liability. Respondent Canadian citizens and residents maintained accounts in a bank in the United States. In attempting to ascertain their Canadian income tax liability for certain years, the Canadian Department of National Revenue (Revenue Canada), pursuant to Articles XIX and XXI, requested the Internal Revenue Service (IRS) to provide pertinent bank records. After the IRS Director of Foreign Operations concluded that the requests fell within the 1942 Conventions scope and that it would be appropriate for the United States to honor them, the IRS served on the bank administrative summonses for the requested information, but, at respondents request, the bank refused to comply. Respondents then petitioned the Federal