The trademark system in the United States is based on the principle of “priority of use.” In most other countries,  the trademark system is based on “first to file.” This difference can cause problems for both US companies operating abroad, and international companies operating in the US.

For a current example, we can look at the challenge facing renowned electric car maker Tesla Motors. Tesla Motors, based in the US, is facing a situation in China where a totally unrelated person has filed and registered a trademark there for “Tesla” and is suing the real Tesla Motors for trademark infringement. Here is a good summary from the Wall Street Journal:  http://blogs.wsj.com/moneybeat/2014/07/10/trademark-headaches-for-tesla-in-china/

Trademark rights are territorial — a registration in one country does not grant trademark rights in another country. Companies operating internationally are advised to look at the countries where they operate to consider filing trademark applications. Candidate countries might include places where they sell products or services, manufacture products or parts, have research and development facilities, have goods pass through during shipping or have as a possible business expansion target.