What you can do, and what has been done in the past, is get a critical mass of large cryptocurrency actors to agree that a protocol change should be applied and that the results of that protocol change are called "Bitcoin". As the Bitcoin Cash folks quickly realized, it's not tenable to try and maintain a disagreement with Coinbase and large miners about about what the Bitcoin protocol is; if you don't want to accept the upgrade, your only practical option is to make a fork and call it something else.