Onchain investigator ZachXBT has publicly challenged the U.S. Financial Crimes Enforcement Network's (FinCEN) estimate that roughly $16 billion in allegedly illicit transactions flowed through crypto exchange MEXC, demanding the supporting data and comparisons with other trading platforms.

His comments came after FinCEN designated MEXC a Primary Money Laundering Concern, a designation that prompted Binance to restrict deposits, withdrawals, and other transactions involving the exchange.

FinCEN, a bureau of the U.S. Treasury Department, enforces anti-money laundering rules across the financial system. The Primary Money Laundering Concern designation is a statutory tool, created under the USA PATRIOT Act, that allows the agency to apply special measures to entities it identifies this way — and, as the market response shows, it can quickly change how other platforms handle transfers tied to the named exchange.

ZachXBT Questions the $16 Billion Estimate

ZachXBT acknowledged that MEXC has historically maintained relaxed anti-money laundering (AML) and know-your-customer (KYC) practices. Even so, he described FinCEN's $16 billion illicit transaction estimate as overstated.

He argued that large centralized exchanges could just as easily show hundreds of millions or even billions of dollars in illicit activity, saying he could identify nine- to ten-figure sums at any major exchange. He asked what share of MEXC's total trading volume FinCEN had classified as illicit, and requested both the underlying data and comparisons with other exchanges.

The size of the estimate carries practical weight because it anchors the designation that other exchanges are now acting on: Binance's restrictions show how quickly the finding translates into blocked transfers for users moving funds between platforms.

The investigator also questioned why offshore exchanges with little or no U.S. presence moved so quickly to restrict transfers involving MEXC users after the designation. He asked who those measures were meant to protect, and raised concerns about possible U.S. regulatory overreach. His remarks were highlighted in a post on X by WuBlockchain.

ZachXBT contrasted the response to MEXC with the treatment of other crypto platforms, specifically citing HTX and KuCoin. In his view, regulators had moved against MEXC while leaving unsanctioned what he called worse offenders.

Binance Restricts Transactions Involving MEXC

Binance announced enhanced compliance measures after FinCEN formally designated MEXC a Primary Money Laundering Concern. The exchange said the restrictions took effect immediately.

Under the measures, users cannot send funds to or receive funds from MEXC through Binance, nor can they conduct other transactions involving the exchange. The restriction covers MEXC Global, its affiliates, and related entities.

Binance said it would reject requests to send funds to MEXC addresses, and that any direct or indirect transaction involving those entities will face further review.

Accounts and Funds May Face Further Review

Binance warned that affected funds and accounts may face temporary restrictions while reviews continue. The exchange added that such activity may breach its Terms of Use.

Whether FinCEN releases the volume breakdowns and peer comparisons ZachXBT requested, how MEXC responds publicly, and whether further platforms adjust their handling of MEXC-linked transfers are the open questions likely to define the next phase of the dispute.