I am in a position where I have been asked to review some code that fixes a problem that I don't believe exists.  

The fixer, who is more senior than me, insists his fix is necessary but it appears to be no more than C++ sophistry to me.  Part of our deployment process is a code review, and as the 2nd highest engineer in a small company I am expected to review changes.

I believe that reviewers are just as responsible for code changes as the original coder, and I am unwilling to accept responsibility for this change. How would you go about rejecting this review?  

Ask for a test case that fails without the change that succeeds with the change.

If he can't produce one, you use that as justification.

If he can produce one then you need to explain why the test is invalid.
