Subpart B of Regulations S is meant to assist in prosecuting money laundering actvities, in addition to being useful in criminal, tax, or regulatory investigations or proceedings. This does not apply specifically to one subset of financial instutions.
Regulation S is issued by the Board of Governors of the Federal Reserve System. The Board "establishes the rates and conditions for reimbursement of reasonably necessary costs directly incurred by financial institutions in assembling or providing customer financial records to a government authority pursuant to the" Right to Financial Privacy Act.
Link to the text: https://www.ecfr.gov/cgi-bin/text-idx?SID=2240159c84d2d3b48422a5185ff69dea&mc=true&node=pt12.2.219&rgn=div5#sp12.2.219.b