What's the rationale behind...

Mutual fund managers not allowed to purchase protective derivative positions?

I assumed the rationale had been that the use of speculative derivative positions significantly increases the leverage of a portfolio; and "Average Joe's" retirement shouldn't be exposed to that level risk. Unfortunately, it seems that by not allowing mutual funds managers to purchase protective puts on any of their long positions, Average Joe's portfolio is often exposed to higher amounts of downside risk. Often times much more than an accredited investor who has access to a "risky" hedge fund.

Please tell me I'm wrong. I'd love to know that "Average Joe's" mutual fund manager has a way to limit downside exposure, other than selling his long stock position.