As the rocket company SpaceX has the largest-ever initial public offering (IPO) today — a blockbuster event that stands to make Elon Musk a trillionaire — stock market regulators quietly handed Wall Street trading giants an extraordinary exemption from consumer protection regulations.

Possibly for the first time ever, broker-dealers are being granted temporary relief from a crucial rule that forces them to maintain cash reserves in a separate account to safeguard customers’ investments if the firms go bankrupt.

While the regulatory reprieve could allow brokerage firms to earn fees from far more transactions amid what was already expected to be a historic trading frenzy, experts warn that eliminating the safeguard could jeopardize the assets of everyday investors caught up in the hype.