Federal prosecutors should be “banging the drum the loudest” to get banks more involved in the nascent cannabis industry, providing visibility and transparency that would help expose any illicit activity, said a former U.S. Justice Department lawyer who’d helped draft guidance for financial crimes related to state legalization of marijuana.

The integration of marijuana businesses into the mainstream financial system would effectively deputize banks to help sniff out money laundering and other illegal activity within the industry, said John Vardaman, now the general counsel to Hypur, an Arizona-based electronic payments and banking compliance software company that helps financial institutions serve state-legal marijuana businesses.