Could you please clarify for me the legality of BitMEX in the United States? I've heard conflicting information about whether or not it's legal for individuals residing in the USA to trade on this platform. Is there any official guidance or regulations that specifically address the use of BitMEX by American citizens? Additionally, if BitMEX is indeed legal, are there any limitations or restrictions that traders from the USA should be aware of? Thank you for your assistance in clarifying this matter.