Common Law Trademark

The common law trademark is something that was very often used in the past. But with today's commerce going global, a company that has used a trademark for years could find themselves in trouble if they do not officially register it with their government.
When common law is referred to a trademark, this means a company has built up it recognition of a particular product in a geographical area over a long period of time. There is some limited protection under state laws, but it is still advisable to register it with the federal government if a company has a trademark.
With trademarks that are governed by common law, trademark infringements are more difficult to establish. Geographical barriers are usually the reason cited in the many court cases that have been pursued. Another common reason these types of infringement cases are not settled in favor of the one claiming to be the first to use it is what did they actually use? Trademarks can be placed on words, phrases, letters, numbers, and symbols. If there is nothing on file somewhere, who is to say what it actually is? In the past, many common trademarks changed over time or were slightly modified. With no official means to record these changes, no precedent has been made in courts.
Today, trademarks that are non-registered are considered common law trademarks and are designated by the symbol ™. Most commonly registered trademarks are used on interstate commerce items while local products can still use a common law trademark for their products