27 CFR § 70.191 - Authorization.
(a) In general. A civil action for the collection or recovery of taxes, or of any fine, penalty, or forfeiture (with respect to the provisions of 26 U.S.C. enforced and administered by the Bureau) will be commenced when the appropriate TTB officer, directs that the action be commenced.
(b) Property held by banks. The appropriate TTB officer shall not authorize or sanction any civil action for the collection or recovery of taxes, or of any fine, penalty, or forfeiture, from any deposits held in a foreign office of a bank engaged in the banking business in the United States or a possession of the United States unless the appropriate TTB officer believes:
(1) That the taxpayer is within the jurisdiction of a U.S. court at the time the civil action is authorized or sanctioned and that the bank is in possession of (or obligated with respect to) deposits of the taxpayer in an office of the bank outside the United States or a possession of the United States; or
(2) That the taxpayer is not within the jurisdiction of a U.S. court at the time the civil action is authorized or sanctioned, that the bank is in possession of (or obligated with respect to) deposits of the taxpayer in an office of the bank outside the United States or a possession of the United States, and that such deposits consist, in whole or in part, of funds transferred from the United States or a possession of the United States in order to hinder or delay the collection of a tax imposed by the provisions of 26 U.S.C. enforced and administered by the Bureau.