Skin Modifications

Alright, so today I've gotten in a debate with a guy in a small facebook community that is ownership of a little League youtuber from my country.

What the debate was about is, ''Are League of Legends skin legal to use without paying them'', and what I mean by this is is it ''Legal'' to modify files in your League of Legends folder by renaming them and putting them as a classic skin even tho they are skins hand made by Riot which can only be obtained by paying a certain amount of money, Riot points to be exact.

Can I get a Rioters point of view, I honestly think this is forbidden it's like walking into a store and taking a bottle of Cola, this is a virtual store but it's practically the same thing, even tho you can do it it's not legal to do it, their perspective was if you can do it then It's legal. This does also include getting skin modifications from MKJogo or MKLol and I'm not talking about League of Legends custom skins made by the community.

Thanks for the help.

Kind Regards, Loneliness