@ThatGuyThere said:
How would you deal with this hypothetical.
You refuse Player A's request for something that needed to be refused. You have the stated yes first policy. So Player A then starts a campaign of Staff is unfair. Said player points out how staff said yes to Thing B C D who were all near the line you have but not quite over it. Up until this point Player A has not shown to be a problem.
Someone in this thread made a point for clarity which was agreeable. To it I'd also add transparency is important.
"Guys, we made the ruling to refuse <X> in this case because $reasons, and when B C and D had a similar-looking we allowed it because $otherreasons. It is our believe $reasons and $otherreasons are sufficiently different to warrant a different approach." Then try to work with Player A to see if you can reach a compromise.
Look, eventually you'll run into players who are unreasonable. Just be sure you're not the kind of staff players run into who is rude and authoritative. So be polite and patient but firm and clear, then if it doesn't work even to the best of your ability and they refuse to take 'no' for an answer it's on them, not you.