RIOT needs to address WHY there is a demand/supply for buying level 30 smurf accounts.
So riot has placed a bunch of handicaps on people that try to power level their smurf accounts to level 30. While they probably did this to make it so that inexperienced players can get more of an exposure to the game before getting to level 30, it has had some pretty big consequences. For one, buying and selling accounts has become huge. In fact, the demand for fledgling level 30 accounts, without wanting to put in 1000 hours, has become so big that entire companies have been created around it. If Riot doesn't like this, which they have said numerous times that they don't, they should address the source of the problem rather than trying to find all of the bot-leveling accounts and banning them.
The problem is that the cost and the man-hours to get to level 30 using xp boosts is much greater than the 15$ cost for a bot-leveled account. Its funny too because Riot can make any account level 30 without basically any effort, so if they made their own business of selling level 30 accounts, they could sell them for all of like 5$. I'm not suggesting they do this, only that Riot can do a lot of things to make getting to level 30 easier.
One thing they can do is give you the ability to link your smurf accounts to your main account, where you can select them from your main, and spend something like 2000 RP to make them level 30. They can also add handicaps like a maximum of 3 smurf accounts per main, or something like getting rid of inactive smurf accounts after a certain amount of time. Either way they have a lot of options, and this seems to definitely be a real issue that needs to be dealt with.
Edit: People have brought up a lot of valid points against my idea, so just scrap it then. Riot can still make it easier for smurfs to level without outright saying smurf accounts are ok. They basically already have a system in place to deal with smurfs at a pre-30 level, normal game MMR. Smurfs usually end up with high MMR, and Riot can use this to reward players that have a high MMR and are still pre-30 with more XP per game. They could also do a thing where if the player wins a game against a team with a higher average MMR, the player will win more XP.