Congress should provide a legal safe harbor for banks that provide services to state-legal marijuana businesses, 19 attorneys general said in a letter today to House and Senate leaders.

The lack of access to banking for state-legal marijuana companies “makes it more difficult to track revenues for tax purposes, contributes to a public safety threat as cash intensive businesses are often targets for criminal activity, and prevents proper tracking of large swaths of finances across the nation,” today’s letter said.

U.S. Attorney General Jeff Sessions recently rescinded a memo that said the federal government would take a “hands-off” approach to enforcement and prosecution in pro-marijuana states that followed certain principles and guidelines.

Twenty-nine states and the District of Columbia have legal medical marijuana, while recreational marijuana has been legalized in eight states.