25 C.F.R. § 700.551 Franking privilege and official stationery.
Title 25 - Indians
An employee is strictly prohibited from using Government franked envelopes with or without applied postage, or official letterhead stationery for personal business. (18 U.S.C. 1719)
Title 25: Indians
PART 700—COMMISSION OPERATIONS AND RELOCATION PROCEDURES
Subpart O—Employee Responsibility and Conduct
§ 700.551 Franking privilege and official stationery.