1. What are Prior Use Rights?

Prior use rights refer to a system that exceptionally allows a person to continue using a trademark even after another party has registered it, provided that the mark was already "well-known" at the time of the other party's application. While this system can serve as a "defensive shield" when receiving an infringement warning from another company, there are extremely high hurdles to maintaining that shield in practice.

2. The "Three High Walls" for Proving Prior Use Rights

To be granted prior use rights, the party receiving the warning must assert and prove the following three requirements:

• (1) Absence of Unfair Intent It is necessary to demonstrate that you are conducting business in good faith, without any intention of free-riding on another person's brand.
• (2) "Well-known" Status at the Time of Application It must be further proven that, at the time of the other party's application, your trademark was already widely recognized among consumers as representing your specific goods or services. Proving this is difficult; simply stating "I have been using it for several years" is insufficient. You must compile a vast amount of objective evidence from that time, such as advertising expenses, sales figures, and articles in industry publications.
• (3) Continuous Use Finally, you must show that you have continued to use the mark without interruption from before the application date to the present.

3. Practical Precautions

Even if prior use rights are recognized, you may still face the following limitations:

• (1) Request for Indication to Prevent Confusion (Article 32, Paragraph 2) Because the prior use right allows a mark identical or similar to the registered trademark to coexist, the trademark owner may request that you add a label to clearly distinguish your business from theirs. This may force you to include disclaimers such as "Not affiliated with Company X" on signs or packaging, which can negatively impact your branding.
• (2) Limitation of Scope The scope of use is limited to the "scope of current use". This means you are not guaranteed the freedom to expand your business or develop new product lines using that mark in the future.

4. Key Takeaway

As illustrated, while prior use rights can serve as a "lifeline" in an emergency, they are by no means an all-powerful right. Even if recognized, risks of business constraints—such as the obligation to display confusion prevention labels—remain. To grow your brand safely and freely, filing an application and obtaining registration as early as possible is the most reliable and cost-effective defense strategy.