19 U.S.C. § 2611 - U.S. Code - Unannotated Title 19. Customs Duties § 2611. Certain material and articles exempt from this chapter

(A) has been held in the United States for a period of not less than three consecutive years by a recognized museum or religious or secular monument or similar institution, and was purchased by that institution for value, in good faith, and without notice that such material or article was imported in violation of this chapter, but only if--

(B) if subparagraph (A) does not apply, has been within the United States for a period of not less than ten consecutive years and has been exhibited for not less than five years during such period in a recognized museum or religious or secular monument or similar institution in the Unites  1 States open to the public; or

(C) if subparagraphs (A) and (B) do not apply, has been within the United States for a period of not less than ten consecutive years and the State Party concerned has received or should have received during such period fair notice (through such adequate and accessible publication, or other means, as the Secretary shall by regulation prescribe) of its location within the United States; and

(D) if none of the preceding subparagraphs apply, has been within the United States for a period of not less than twenty consecutive years and the claimant establishes that it purchased the material or article for value without knowledge or reason to believe that it was imported in violation of law.