(archaic) On which no customs duties have been paid.
1760, Tobias Smollett, Continuation of the Complete History of England, London: Richard Baldwin, Volume 3, p. 331,
[…] a bill was prepared […] importing a continuation of several laws, namely, the several clauses mentioned of the acts in the fifth and eighth of king George I. against the clandestine running of uncustomed goods […]