It's never been done because it will invalidate literally every single transaction ever made. Every transaction spends coins that were either generated by the pre-mine, or generated in blocks built on top of the pre-mine. The only other way is to add code that invalidates transactions made after a certain blockheight that spend coins from the pre-mine coinbases, but a) there's nothing stopping the founder from moving his coins before that blockheight, if he hasn't already done so, in which case there's nothing you can do to stop him from spending his coins, and b) your users will be quick to realise that if you're going to add rules preventing people from spending certain coins, none of their coins are safe either.
You just have to accept the fact that the founder has a shit-tonne of coins that he didn't earn, there's nothing you can do about it, and it's all your fault for agreeing to use a pre-mined coin in the first place.
Topic: How to invalidate pre-mined blocks? (Read 700 times)
as you said: create a fork that will be bigger then the original blockchain (that nobody is mining currently i presume) and merge it. your blockchain will be bigger and network will adopt it. can't give you an example tho, never saw it done by someone 
How about just restart the coin?
I'm working on a coin that has 8000 blocks premined by one of the founders. This founder left the project and now we want to invalidate those premined coins. I thought about creating a fork or something else, but couldn't find an example or something like this already done in other coin. Could someone please help?
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