Gerrit (http://code.google.com/p/gerrit/) won't allow you to push directly to master branch. Instead you have to push to a 'review' branch.
Typically you're told to indicate 'review' branch on every push, e.g.
$> git push origin refs/for/review
You can make your life easier by setting up push branch in config/.git file:
$> vi .git
push = HEAD:refs/for/review
Note: The examples above assumes your remote repository is nicknamed 'origin'.