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19 U.S. Code § 1752 - Entry of articles for fairs

Any article imported or brought into the United States—
(1)
which is in continuous customs custody, covered by a customs exhibition bond, or in a foreign trade zone, and
(2)
on which no duty or internal-revenue tax has been paid,
may, without payment of any duty or internal-revenue tax, be entered under bond under this section for the purpose of exhibition at a fair, or for use in constructing, installing, or maintaining foreign exhibits at a fair.
Statutory Notes and Related Subsidiaries
Immunity From Seizure Under Judicial Process of Cultural Objects Imported for Temporary Exhibition or Display

Presidential determination of cultural significance of objects and exhibition or display thereof in the national interest, see section 2459 of Title 22, Foreign Relations and Intercourse.