The monarchy in the UK doesn't hold any authority to pass legislation. They are merely figureheads that stay neutral, well publicly silent anyway, on political matters.
If Charlie did in fact say this it would have to go through Parliament.
I don't know where this started but it's a nonsense story.
P.S. I'm not a Royalist.
RE: King Charles Going After Money Laundering And Terrorism By Granting Authority To Seize Cryptocurrenc