In the weeks after the 9/11 attacks, the US moved to choke off funding for terrorists and other global bad actors. As part of the Patriot Act of 2001, it required financial firms of various sorts to implement anti-money laundering programs similar to the ones in place at banks.

Twenty years later, the envisioned united front against dirty money has failed to materialise. Private equity firms and hedge funds with trillions of dollars in assets have escaped the anti-money laundering mandate because the US Treasury — under Republican and Democratic presidents — has yet to issue final rules applying the law to such investment advisers.

The results are worrisome on multiple levels. Anti-corruption campaigners claim the delay has opened a back door into the US financial system for criminals and kleptocrats the world over. Compliance experts fret that banks and brokers have been left to shoulder the burden of anti-money laundering enforcement — even as they compete on today’s Wall Street against private equity groups and hedge funds in businesses including lending.