So I just made an EUW account and found hey this ping is better than NA fancy that and well I am leveling up my account maybe 3 or 4 games a day and everyday or at least every 7 games there is one player who to me behaves like a bot. This player would first of only move every 3 or so minutes always move in one direction regardless the terrain or turrets or whatever would never buy any items till the absolute end of the game and the items would never be good for that champion. This kinda pisses me off but I do not know if its legal or not so is it and when you find a player that does what should one do?
J. Using any unauthorized third party programs, including but not limited to "mods," "hacks," "cheats," "scripts," "bots," "trainers," and automation programs, that interact with the Software in any way, for any purpose, including, without limitation, any unauthorized third party programs that intercept, emulate, or redirect any communication between the Software and Riot Games and any unauthorized third party programs that collect information about the Game by reading areas of memory used by the Software to store information;
So while I'm pretty sure It's legal (you won't go to jail for using bots) it's violiting the TOS of League and thus it can get your account banned. If you see a player botting you can report him for any reason but add a comment to your report so they know it's a bot and not a normal report.
I usually report those players as an unskilled player with a comment like "Might be a bot" or something like that since you can't be 100% sure whether or not they really are botting. A lot of players are also just so unimaginable bad that it looks like a bot.