Assume a user is not allowed to push to a specific branch. That user made a new commit on that branch in a local repository, and added a tag onto the commit.

Pushing the tag will cause the commit to be pushed as well, though the commit wouldn't show in the history of the branch, but rather it will show when the specific commit URL is searched.

Steps to reproduce:

1. Create new branch (and lock it on bitbucket).
   With a user who is not allowed to push to that branch:
2. Make a commit
3. Add tag on that commit
4. Push to bitbucket
5. Go the url for that specific commit

It will show in a specific commit URL:
https://bitbucket.org/username/repositoryname/commits/xxxxxxx

But it won't show up in the branch commit history log:
https://bitbucket.org/digipolisgent/username/repositoryname/commits/branch/branchname