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I don't know why either, but the fact that they CAN is not a good thing.

Yes it's legal, but is it wise? Most of the time you will end up losing in the withdraw fees alone. Unless you're arbitraging a large amount, it might not even be worth it.

Is it wise? Depending on the difference I would say yes, if you rise and repeat over hours its good money. Yeah, its something that would require alot to sit on exchanges.

@freedomcoim have you tried it?

No I have not, just speculating on reasons why they would stop it. Ripple is trying to be complaint with banks, so maybe its a requirement of one of the banks?