International Trademark Law is a costly and long winded process - your client will need a specialist Lawyer/Attorney and deep pockets. A designer/originator also has rights to how a client uses that work for their business, it is one thing to design a logo for a local business for xxxx$, but a completely different matter if a client is going to the expense and trouble of TM or R for that logo.
At this post there are a couple of useful links to various online destinations for copyright questions.
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