Ripple is not a cryptocurrency !
It is an electronic token, issued by a company. Ripple Labs Inc.
They can do what they want, they are in the USA, so they can receive national security letters - they may have received some already.

They can create tokens from thin air and basically they are a FINANCIAL INTERMEDIARY
Just like Wells Fargo blocked wire transfers to exchange because Uncle Sam wanted it, they could (be forced) do the same....they are unsuitable as an investment!