What is the reverse onus law?

Can you please explain what the reverse onus law is in simple terms? I've heard it mentioned in the context of cryptocurrency and finance, but I'm not entirely sure how it applies or what its significance is. Is it a legal principle that applies specifically to the crypto space, or is it more broadly applicable? I'd appreciate any insight you can provide on how this law works and the potential implications it may have for individuals and businesses involved in cryptocurrency transactions.