Rather than block investors from complex ETFs, another, perhaps preferable, approach would be to require that explanations of complex investments be written clearly, in simple English, and that the consequences of an investment, including risks, in those ETFs be clearly spelled out. That would allow investors who would like to use ETFs as part of their portfolio, and understand the consequences of doing so, to use these "complex" instruments. If an ETF provider is unable to explain their instrument in plain English, then their instrument should be unavailable.