SEC has raised legal concerns over REX and Osprey's Staking ETF plans involving Ethereum and Solana.SEC's Associate Director expressed unresolved questions regarding the legitimacy of the products under the Investment Company Act of 1940.The ETF structure has been described as relying on legal and regulatory workarounds, but SEC's response indicates discomfort.The regulatory pushback highlights the challenges faced by crypto-linked investment vehicles like staking-based products in mainstream markets.