Unregistered trade marks can be protected by the common law action of passing off. You must prove goodwill or reputation in the unregistered trade mark and must prove that the other person misrepresented his/her goods or services to be the goods or services under the unregistered trade mark and that person's use of the trade mark will cause you damage. Passing off is usually a more difficult action to bring than an action for infringement of a registered trade mark.
For example, the owner of a well-known trade mark may seek an injunction against the use of an identical or similar trade mark by another person under certain circumstances. Also, the owner of a well-known trade mark may be entitled to oppose the registration of an identical or similar trade mark by another person under certain circumstances. Details of the relevant protections for well-known trade marks can be found in the Trade Marks Ordinance, Cap.559.