2 U.S.C. § 1881a
At the request of an immediate family member of a firefighter, law enforcement officer, member of a rescue squad or ambulance crew, or public safety officer who died in the line of duty, the Representative or Senator of the family may provide to the family a Capitol-flown flag, together with the certificate described in subsection (c).
A Capitol-flown flag provided under this section shall be provided at no cost to the family.
The certificate described in this subsection is a certificate which is signed by the Speaker of the House of Representatives and the Representative, or the President pro tempore of the Senate and the Senator, providing the Capitol-flown flag, as applicable, and which contains an expression of sympathy for the family involved from the House of Representatives or the Senate, as applicable.
2 U.S.C. § 1881a