My understanding of the law is that stolen goods remain the property of the original owner, no matter what subsequently becomes of those goods. If I buy a TV on ebay and it then transpires that the seller had stolen it, I would have to surrender the TV back to the legal owner, regardless of the fact that I had paid for it, in good faith. I might even find myself prosecuted for “receiving stolen goods.”
It appears that this simple principal does not apply to political parties. In 2005 the Lib-dems accepted a donation of 2.4 million pounds from a certain Michael Brown. It was subsequently revealed that this money had been stolen, and Mr Brown has been sentenced to 8 years inside for the theft. Unfortunately he has skipped the country.
You would have thought that, in the spirit of the law the Lib-dems would have to give that money back to be returned to the rightful owners. You would be wrong. The electoral commission ruled in 2009 that the Lib-dems could keep the money as it had been accepted in good faith. One rule for us, an entirely different rule for them.