From the Manual:
Mere receipt of any law enforcement inquiry, does not, by itself, require the filing of a SAR by the bank.
Nonetheless, a law enforcement inquiry may be relevant to a bank's overall risk assessment of its customers and accounts.
For example, the receipt of a grand jury subpoena should cause a bank to review account activity for the relevant customer.
It is incumbent upon a bank to assess all of the information it knows about its customer, including the receipt of a law enforcement inquiry, in accordance with its risk-based BSA/AML compliance program.
The bank should determine whether a SAR should be filed based on all customer information available.