EU single market: French liquor and trade barriers
15 March 2013 Last updated at 14:07 GMT
The EU seeks to protect one of its core principles - the single market - which aims to offer a level playing field for businesses across the continent.
Adam Fleming looked at the history of the rules and the role of a French liquor in bringing down trade barriers in his Politics Europe film.
The rules were in the news again this week as the European Court of Justice said Ireland was not charging the correct rate of VAT on the artificial insemination of horses.
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