"Hey, I gave real money to this guy and agreed to accept magic beans in return. Now I have discovered that I can no longer redeem these beans for cash"
"Hey, I gave real money to this guy who sold me what falls under SEC regulation as a security due to the Howey Test [1] [2]. I would like them investigated for securities fraud."
It's easy. I've filed such complaints myself. I've bought securities knowingly defective to file the complaints when I was aware fraud existed. Bitcoin and Ethereum fail the Howey Test, but if someone steals them from you, you can still legally pursue for the theft of your digital commodity (or tangentially, the laundering of those funds if the theft and laundering are done by separate parties [3]).
The wheels of justice turn slowly, but grind exceedingly fine.