9 CFR § 96.5 - Instructions regarding handling certified animal casings.
(b) Casings offered for importation into the United States shall remain in customs custody at the port until released by an APHIS inspector for admission into the United States or otherwise disposed of as required by this part.
(c) The provision that under certain conditions casings which have been offered for importation shall be exported, shall be construed to mean the removal of the casings from the United States or its possessions.
(1) The provision that under certain conditions casings be destroyed shall be construed to mean the treatment or handling of the casings in a manner to take away completely the usefulness of them as by tanking or incineration.
(2) The provision that under certain conditions casings shall be disinfected and denatured shall be construed to mean such treatment and handling as will be prescribed by the Administrator, Animal and Plant Health Inspection Service (APHIS) to free them from pathogenic substances or organisms, or to render such substances and organisms inert; and that the nature of the casings be changed to make them unfit for eating without destroying other useful properties. For instance, each casing may be split throughout its length and after disinfection, as above indicated, be released for industrial use.
(d) Dried intestines offered for importation into the United States for use as gut strings or similar purpose are not regarded as animal casings within the meaning of this part. Such dried intestines are classed with tendons, sinews, and similar articles and are subject to the provisions of part 95.