I am not sure about foreign goods, but goods manufactured in the US are NOT required to have UL approval. This is strictly a marketing requirement, although it should be a requirement to have UL or other third party safety approvals.
Go to UL.com and get some contact numbers and ask them if they have heard of this and then contact a customs agent and ask them the same question. It could be a 'customs' requirement but I doubt if it is a requirement just because it is imported.