accounts with a broker

The government has nothing to do with it. Many times, large brokerages take private insurance from Securities Investor Protection Corporation (SIPC) – to cover some risks (not investment loss risk though). In case of losses due to severe malpractice, the only recourse is legal action (sueing the brokerage, usually class action by lawers who specialize in securities fraud law)

see http://www.finra.org/InvestorInformation/InvestorProtection/SIPCProtection/index.htm

for SIPC insurance offered by FINRA (Financial Industry Regulatory Authority, Inc.)