I know for sure these are not regulated or illegal in the UK and no courts in the USA have ever decided they would be classed as a security in terms of any case law, unless you know of any?
The SEC has been going after crypto ponzis for years, see my signature for one example. They have also issued warnings regarding ICOs and enforcement is likely to come.
But ponzis are illegal anyway, regardless of securities violations or lack thereof.
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For crypto-currency ICOs heading center is the "British Indian Ocean Territory", home of "Diego Garcia" NSA base as the next incognito Crown jewels to compete Wall Street IPOs.