41 CFR 304-4.1: -4.1 Alternative authorities for accepting non-Federal source travel expense payments.

Agencies may accept payment for travel expenses to events other than meetings from a non-Federal source pursuant to an agency gift statute or similar statutory authority. However, this part is the only authority agencies may use to accept (or authorize an employee to accept on the agency's behalf) payment for travel expenses from a non-Federal source to attend a meeting.