Crash course on trademarks: The procedure for getting a trademark
In most countries, trademark rights are obtained through a registration procedure. Like with most other intellectual property rights, trademarks are national affairs. This means that a trademark must be registered separately in all countries where the applicant would like to have trademark protection. Various treaties exists that ease this situation somewhat.
To register a trademark, the applicant typically sends in a form indicating the trademark (for example the word or words that should be protected, or a picture of the logo or color that should be protected) and the goods or services for which the protection is desired. In most countries, these goods and services must be indicated using the classes and/or specific indications as defined in the Nice Agreement. By referring to these class numbers, it is clear to everybody what the trademark protects.
In some countries, registration is automatic and there is no evaluation of whether the trademark is actually valid. In other countries the trademark office checks the register with earlier trademarks to see if there are possible conflicts, and also evaluates whether the trademark is distinctive for the goods and services indicated. If the trademark is subsequently approved by the trademark office, there sometimes follows a period during which third parties can file an opposition against the trademark. For example, somebody else may feel he has an older trademark right that is confusingly similar to the new trademark, or he may consider the new trademark to be generic for one of the goods or services indicated.
After a successful registration, the trademark holder is then able to enforce his trademark against third parties who use it in commerce. A trademark right can last forever, but it must be renewed regularly (typically every 5 years). This way, unused trademarks lose their protected status. Of course, anyone can file a new trademark application later on. If the former trademark in the meantime has not become a generic or descriptive term in the mean time, the new application will be accepted.
Even after being accepted by the trademark office, a trademark can always be annulled in court if the court finds that the trademark is or has become descriptive for the goods or services for which it was registered. Additional, it is required that the trademark holder actively uses his trademark in commerce for his own goods and services. If there has been no use in commerce for a sufficiently long period of time (typically 5 years), the trademark can also be declared invalid.
It is worth noting that some countries, in particular the United States, also provide trademark rights for unregistered trademarks. The mere use in commerce of a particular sign can turn that sign into a trademark, which others may not use for the same types of goods and services. Such unregistered trademarks are sometimes indicated with the suffix TM, while registered trademarks are indicated with the famous R in a circle ®.
Claiming that a term is a registered trademark while it is in fact unregistered is usually illegal, especially when you make such a claim commercially. Of course no one will object if you jokingly use the ® symbol with something, e.g. to indicate it's a distinctive phrase with a special meaning ("This is a Bad Thing®"). But if you add the ® to your website's name, or to a free service you offer, you could get in trouble.