12 USC 633 - Potential liability on foreign accounts

(a) Exceptions from repayment requirement 
A member bank shall not be required to repay any deposit made at a foreign branch of the bank if the branch cannot repay the deposit due to
(1) an act of war, insurrection, or civil strife; or
(2) an action by a foreign government or instrumentality (whether de jure or de facto) in the country in which the branch is located;

unless the member bank has expressly agreed in writing to repay the deposit under those circumstances.

(b) Regulations 
The Board and the Comptroller of the Currency may jointly prescribe such regulations as they deem necessary to implement this section.