The world’s largest issuer of stablecoins has frozen 326 wallets containing $435 million worth of Tether (USDT) for US authorities. The assets were frozen to assist law enforcement agencies, including the U.S. Department of Justice (DOJ), the Federal Bureau of Investigation (FBI), and the Secret Service.

On Dec. 1, the company implemented a “wallet freeze policy” to help law enforcement agencies combat the illegal use of stablecoins. Calling it a “historic milestone,” Tether said the “simple but effective” policy involves freezing all wallets on the Office of Foreign Assets Control’s (OFAC) Specially Designated Nationals (SDN) list.

“By extending our sanctions controls to the secondary market, we are setting a precedent in the industry by being forward-thinking and vigilant,” the company said.

The Secret Service was recently connected to the platform and is currently working to connect with the FBI. The stablecoin issuer has also helped the DOJ “thwart unscrupulous players and help victims recover.”

In its 4-page November letter, Tether listed all of its ongoing efforts to prevent USDT from being used for nefarious purposes. In particular, the letter cited having a “strong” Know Your Customer (KYC) and anti-money laundering (AML) program that is as strong as those in place at “sophisticated financial institutions.”

Tether cooperates with 19 jurisdictions around the world and assists in ongoing investigations, in some cases actively offering information to law enforcement. For example, Tether has worked with Israel’s anti-terrorist financing agency NBCTF to identify and freeze wallets linked to Hamas and other terrorist organizations. The company intends to continue working with the agency to prevent the illegal use of USDT.