Add user rights to limit access to certain users (and give all rights to others)

The goal is, rather than give access to all users to the merge and refuse most cases if they're not the administrator (which is irrelevant later as SUPERUSER_ID is used), to give to a certain group 'Partner Merge' merging rights as if they were the administrator, and hide/deny merges otherwise.
Why is this removed while the file still exists?