http://www.legislation.gov.uk/id/eut//teec

PART THREEUNION POLICIES AND INTERNAL ACTIONS

TITLE IIFREE MOVEMENT OF GOODS

CHAPTER 1THE CUSTOMS UNION

Article 30(ex Article 25 TEC)

Customs duties on imports and exports and charges having equivalent effect shall be prohibited between Member States. This prohibition shall also apply to customs duties of a fiscal nature.