In 2007 I raised the issue of the code of ethics for dealers in antiquities. I reproduce part of the earlier post here:
If you read the UNESCO International Code of Ethics for Dealers in Cultural Property which was endorsed in November 1999 (now helpfully reproduced in Legal and Practical Measures Against Illicit Trafficking in Cultural Property: UNESCO Handbook (2006) [pdf]; the code is mentioned in the UK Department of Culture, Media and Sport document, Ministerial Advisory Panel on Illicit Trade (2003) section 104) you will find that Article 1 states
Professional traders in cultural property will not import, export or transfer the ownership of this property when they have reasonable cause to believe it has been stolen, illegally alienated, clandestinely excavated or illegally exported
I would also draw attention - as I did in 2007 - to the Dealing in Cultural Objects (Offences) Act 2003 [detail]. Some key elements:
"A person is guilty of an offence if he dishonestly deals in a cultural object that is tainted, knowing or believing that the object is tainted."There is a section on the Meaning of “tainted cultural object”.
"It is immaterial whether ... the removal or excavation was done in the United Kingdom or elsewhere".