Copy/Paste from my No Johns ruleset post I've been working on
1. Prevent overly randomized results – One primary objective of any competitive ruleset is to ensure consistent results. Consistent does not mean that the same/best person wins every time - consistent is just consistent. There is always variation in results, even before random factors come into play. We have to acknowledge that Melee is a game that does include a degree of randomness. Decisions under this criteria have to meet some arbitrary threshold. In this case I’ve selected something that is considered widely acceptable by the community - the results randomization generated by the computer’s selection of Peach’s turnip pull - as my standard (referred to as the Turnip Threshold). Any effect that is less significant than this, then, should be allowable.
2. Single-character or single-strategy brokenness – Stages such as Hyrule, with run-away projectile camping being unbeatable, fall into this category. If two characters are viable, then clearly neither is broken and you have options available to you.
3. Unavoidable glitches that impede gameplay – Stages like Brinstar Depths, through which your character can randomly fall through any part of the stage, were banned for this reason. FoD is banned in teams because the frame drop messes with people. I never thought Mute frame drop was bad enough to warrant it, but some do.
That's my ban criteria for basically anything...stages, glitches, etc. But I'm still working on it...not entirely happy with how it's explained yet.