The Hong Kong financial regulator the Securities & Futures Commission of Hong Kong (SFC) announced a new regulatory plan, according to which all cryptocurrency companies that allow trading will have to apply for a license if they wish to continue operating in its jurisdiction.
Up until now they operated based on an opt-in approach, as cryptos like BTC and Ethereum did not classify as securities. To clarify, the current regulation did cover all companies that deal with cryptos, but certain companies could be exempt from it by claiming that what they deal in is not classified as a security. Several of the cryptocurrency exchanges operating in Hong Kong operated in this manner. Some of the biggest exchanges in the world operate there, but not all of them have filed for a license.
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With China establishing more and more control over Hong Kong this was inevitable.