U.S. derivatives regulators approved restrictions on how brokers can invest customer funds, acting on a delayed rule after as much as $1.2 billion went missing before MF Global Holdings Ltd. sought bankruptcy protection.

The Commodity Futures Trading Commission voted 5-0 today to limit how brokers invest clients’ margin in money market funds, and ban investments in foreign sovereign debt and in-house transactions such as repurchase agreements.

CFTC Commissioner Bart Chilton, one of three Democrats on the five-member panel, pushed for completion of the measure, which he dubbed the “MF rule.” CFTC Chairman Gary Gensler said the regulation is “critical for the safeguarding of customer money” by preventing in-house repurchase transactions.