27 C.F.R. § 26.101
(b) The excise taxes collected on beer of Puerto Rican manufacture shall be deposited in the Treasury of Puerto Rico only if the sum of the cost or value of the materials produced in Puerto Rico, plus the direct costs of processing operations performed in Puerto Rico, equals or exceeds 50 percent of the value of the beer when it is brought into the United States.
(Aug. 16, 1954, Chapter 736, 68A Stat. 907, as amended (26 U.S.C. 7652))
[T.D. ATF-206, 50 FR 15888, Apr. 23, 1985]