What is the Marvel Cinematic Universe if not cinema's all-time greatest conflict between good and evil? And yet despite the ever-expanding, fantastical nature of the franchise, the world is still dictated by laws, regulations, oaths, and what have you.
Just because somebody can manipulate the very fabric of reality itself at a moment's notice, it doesn't mean their life isn't subject to a series of rules - or, at least, guidelines - which they're required to follow for one reason or another.
There is, however, a sure clash between a super-powered character's ability to do basically anything and the universe's need for order, for their powers to be checked in some form.
And it's fair to say that some of these rules are more reasonable and sensible than others: there are many that just seem ludicrous, paradoxical, and otherwise silly for anyone, human or super, to follow.
It's impossible for such contradictions not to arise in an enterprise as vast and all-encompassing as the MCU, because there's no doubt that real-life superheroes would create major legal, moral, and ethical quagmires in our own world.
Whether it makes sense or not, these are the rules that the MCU's biggest heroes and largest groups are required to follow...
10. Celestials Don't Interfere In Human Affairs
Let's kick things off with one of the most common complaints in the MCU, that as the franchise has expanded its roster of ultra-powerful superheroes, it's become tougher to explain why these beings haven't helped out the frontline Avengers in major Earth conflicts.
In the case of the Celestials, however, an attempt has been made to hand-wave this "plot hole" by affirming that the Celestials and their adjacent creations are bound by an oath not to interfere in human affairs.
In Marvel's What If? animated series, The Watcher (Jeffrey Wright) reiterates that he cannot and will not interfere in the events he observes, while in Eternals the Celestial Arishem will only allow the Eternals to involve themselves in earthly affairs if the Deviants are part of a conflict.
This flimsy rationale becomes even more twisted when it's later revealed that Arishem actually posted the Eternals on Earth to kill the Deviants and ensure the planet became populated enough for the Emergence to happen, which would in turn birth the new Celestial Tiamut.
Granted, Celestials are so far beyond the realm of a typical living thing's experience that we can't imagine this oath bothers them all that much, what with the universe being as endlessly vast as it is and humanity a mere speck on it.