You probably won't find the whole text - in hard copy, it runs to three printed volumes!
I don't know the exact details of the components used to make a Raspberry Pi, but I have spoken to staff at HMRC and Business Link, and they confirm that finished items such as the Raspberry Pi attract no import duty, whereas many of the components do if imported seperately.
The details of this are not written in any law as such, but covered by the tariff. It doesn't really need a specialist lawyer to understand - it is more the remit of an import/export agent.
If you wish to persue this further, then I will provide a few links which may help.
Similar information is available from all EU Governments.