The ICBA is one of the largest banking advocacy organizations in the U.S., typically representing smaller institutions. It also played a significant role in pushing back against the Digital Asset Market Clarity Act that failed to advance in the U.S. Senate last month — in part due to the bankers' objections that its stablecoin provisions didn't protect them against direct competition with the deposit accounts that are core to their businesses. Now, the group is targeting the trust charters crypto firms are pursuing as an entry point into the U.S. banking and payments system.

"Congress did not create the national trust charter as a side door into the banking system for crypto firms seeking the credibility of a federal bank charter," ICBA President and CEO Rebeca Romero Rainey said in a statement, adding that the firms don't get the same obligations on such things as capital, liquidity, supervision and the need for insurance from the Federal Deposit Insurance Corp.

Asked for comment by CoinDesk, an OCC spokesperson said the agency "does not comment on litigation."

The OCC has been granting a steady stream of trust charters to crypto firms, however those companies don't operate under the same business model or intend to offer the same services as typical community banks. For instance, they don't offer the same kind of cash deposit accounts for which FDIC insurance is designed and required.