First, using mixer has a chance of getting dirty bitcoin in return regardless of mixer is legal or illegal in a place.
Please stop promoting the idea that taint exists. I consider making people believe it exists an attack on Bitcoin, and it may very well be the only way for governments to stop Bitcoin. Don't fall for it.
You don't know the origin of the bitcoin.
You don't know where your change in a supermarket came from either. Even better: you can be pretty sure there's cocaine on it. But it doesn't matter, as money is fungible. Without fungibility, money is useless, and that's why this "taint" BS is nothing more than an attack on Bitcoin. Don't believe it, and it doesn't exist.
I can't remember any mixing site which ensure giving clean bitcoin, newly mined bitcoin.
See:
There are multiple types of services:
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Second - newly minted coins. You deposit some funds and you receive "clean, newly minted coins fresh from miners genesis block". Good part is newly minted coins out of coinbase (not this one) should have no history and should be accepted by anyone accepting Bitcoins. Bad part is that none of services that advertises by that does that.