I have recently started watching *Dragon Ball Z*(Remastered Edition)\* after a long break. There is this scene in S01E21 (*Counting Down*) in which Master Roshi and others summon the dragon to wish Goku back. Just before they can wish him back, Oolong (the pig) says:

> 
> Excuse me, Mr. Dragon could be possibly destroy the Saiyans that are on the way to Earth right about now.
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> 
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to which the dragon replies:

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> Your wish cannot be granted because the guardian of Earth created me. I cannot grant a wish which exceeds his power.
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Now, this has put me into dilemma. If the dragons' power was only limited to Earth, why was everyone around the universe after these Dragon Balls?

Here are few questions that bug me:

* When the dragon says "wish which exceeds his power", does he mean that he can only use his powers on/for the Earthlings?
* If yes, how could they wish Goku back, because technically, he is not born on Earth?
* If not, why did destroying the Saiyans exceed the dragon's power?
* Everyone around the universe was searching for Dragon Balls because they could fulfill anyone's wish. Does it mean that it is not mandatory to be an Earthling, but it's compulsory to be on Earth to have your wish granted by the dragons?
* If yes, why didn't they ever wish to destroy the enemies after they had landed on Earth and within the effect of the dragons' power?