Can Exotic and Miniature Bully Varieties Be Registered?
https://dogownerguide.evergrovio.com/posts/can-exotic-and-miniature-bully-varieties-be-registered
I've been researching this for a while because I have a miniature bully, and the rules vary a lot by registry. Some kennel clubs accept them if they meet breed standards, while others specifically exclude non-standard sizes. You really need to check with the specific organization you're interested in registering with, as their policies differ.