In the United States, trademark rights flow from use, not registration. A business may be afforded a certain level of trademark protection in its geographic area simply by being the first to use a mark in commerce in connection with its goods or services. However, any unregistered or "common law" rights may be limited geographically. There are critical differences between common law trademark rights and trademark rights obtained via a federal trademark registration with the U.S. Patent and Trademark Office (USPTO). As discussed in this article, priority battles can ensue over conflicting trademark priority dates. In addition, a first user's trademark rights can be "frozen" in a particular geographical area by a later or second user in certain circumstances.