To start, requests don't need a "legal basis" I can request that you paint me a picture, this has no legal basis. But you are still free to accept and paint a picture, maybe I request a picture in exchange for something else, etc.
And in terms of pursuing legal action, You pursue legal action like this to determine if someone is in the right or wrong. It starts out as "undecided"
Lets say you hire me to build a shed. And when the shed is built, There is a misunderstanding about how you initially wanted the shed. So you are unhappy with the shed and refuse to pay for it because your position is that it's not what we agreed upon, and thus you won't pay.
I however disagree and say that it actually is what we agreed upon, and I want my money. From your point of view, you are right, and you have done absolutely nothing wrong, and I have done something wrong.
From my point of view, I have done nothing wrong, and you have in fact done something wrong by not paying me because you didn't pay enough attention to the initial agreement.
At this point, you can't just say "No law has been broken because I'm in the right, so legal action can't be pursued"
I then serve you with a lawsuit, Now you have to respond (show up and defend yourself) to the lawsuit or you will lose by default. In the lawsuit, the court will decide who is actually right and who is actually wrong all along.