WASHINGTON (Reuters) - With his cult following, Telsa boss Elon Musk has amassed considerable power to move markets with his musings, but murky rules make it difficult for regulators to rein him in.

The celebrity CEO, who boasts more than 54 million Twitter followers and has a devoted constituency on Reddit, has whipsawed the cryptocurrency market and sent some stocks soaring this year with a series of tweets and business announcements.