Minn. Stat. § 333.30: MARKS ACQUIRED AT COMMON LAW.

Nothing herein shall adversely affect a person's rights or the enforcement of the rights in a mark acquired in good faith at any time at common law, except that the rights as against the registrant of the same or confusingly similar mark are limited to the areas of the person's use established prior to the registration date and areas in which the person's mark has become known prior to the registration date.