Trademarks that have acquired distinctiveness locally have nevertheless protection against trademarks that can be confusingly similar. This means that you can prevent others from registering a trademark that you have established locally.

To prevent others from registering your locally established trademark, you can file a protest during application processing or an opposition within three months after the trademark has been registered.
You can read more about protest and opposition on the page about "Appeal Options"

If you submit a protest or an opposition, you must document that you have acquired an established right to the trademark through use. It is important to be aware that the Norwegian Industrial Property Office will then carry out its usual assessment of the likelihood of confusion when we assess whether a trademark is in conflict with an established trademark.

If the trademark has been registered for more than three months, the period of opposition has expired. In such cases, you cannot submit a claim that the registration is invalid on the basis of a trademark that has acquired distinctiveness locally.

Legislation

See Trademarks Act, Sections 16 and 35.