Summary

Centralized stablecoins (USDT, USDC) can freeze assets via contract-layer blacklist functions, but on public blockchains a freeze is an ordinary transaction that must compete for execution priority. When a sanctioned entity’s transfer and the issuer’s freeze transaction race for inclusion in the same block, outcome is determined by block producers’ economic ordering decisions — not regulatory authority. Wu et al. (2026) call this Sanction-Evasion MEV (SE-MEV): the value extracted from the race between compliance enforcement and evasion.

The Core Vulnerability

Contract-layer authority ≠ consensus-layer enforcement

A blacklist invocation is an ordinary on-chain transaction. In Ethereum (PoS), a sanctioned entity can submit a transfer in the same block and compete directly for execution priority. The entity with higher MEV-weighted priority wins — not the regulator.

The gap is empirically real: on multiple documented occasions, the issuer’s freeze transaction entered the mempool first, yet the evasive transfer was confirmed on-chain first.

Empirical Dataset (Nov 2017 – Aug 2025)

From the first comprehensive on-chain sanctions enforcement dataset for Ethereum USDT and USDC:

MetricUSDTUSDC
Sanctioned addresses drained to zero before enforcement7.3%18.7%
Total assets frozen (nominal)Part of $1.5B+ totalPart of $1.5B+ total
Evasion trajectoryEscalating arms raceEscalating arms race

Escalating arms race trajectory:

  1. Early era: issuer out-of-gas failures (basic ordering failures, no evasion intent)
  2. Public gas auctions: evader and issuer compete via priority fees in public mempool
  3. Private order flow: evader submits to private relays; freeze goes public → evader wins
  4. Direct proposer bribery: evader bypasses public fee mechanism entirely; pays proposer directly

Game-Theoretic Model

Three main results:

  1. Compliant issuers cannot stay outside the MEV market: in a reactive sanctions environment, issuers who don’t participate in ordering infrastructure will lose the races

  2. Fixed participation costs → concentrated evasion: high entry costs push evasion toward a small set of specialized, MEV-aware actors. “Amateur evaders” are priced out; professional searchers internalize evasion as a revenue stream

  3. MEV tax grows monotonically with regulatory penalties: as regulators intensify enforcement, the value of a successful evasion increases → block proposers extract a higher implicit tax. Enforcement becomes increasingly expensive

Equilibrium implication: repeated interaction creates structural incentives for issuers to vertically integrate into block-building infrastructure. If Circle (USDC) owns a block builder, it can guarantee freeze transactions land before evasive transfers.

Structural Consequences

For Stablecoin Issuers

  • Cannot maintain sanctioning authority without participating in MEV infrastructure
  • Either integrate with block builders/relays or accept ~7–19% evasion rate
  • “Contract-level authority” is not a security property on public blockchains

For Block Builders and Validators

  • Willingness to process evasive transactions is economically rational
  • Builder who excludes SE-MEV opportunities loses revenue to competitors
  • Creates tension with OFAC-compliant relay policies (which filter users’ transactions, not issuers’ enforcement)

For Protocol Design

The same structural vulnerability applies to any privileged action that must be implemented through ordinary transactions:

  • Emergency pauses (DeFi protocols)
  • Governance interventions
  • Judicial freezes (future CBDC enforcement)
  • Oracle updates vs. oracle frontrunning

Connection to FOCIL and CROPS

FOCIL (EIP-7805) specifically addresses censorship resistance from a different angle — ensuring valid transactions are included despite builder censorship. SE-MEV exposes the inverse: even with perfect inclusion guarantees, ordering determines regulatory outcomes.

FOCIL inclusion lists guarantee a freeze transaction enters the block. But if the evader’s transfer also enters the block, the ordering within the block still determines who wins. Inclusion ≠ ordering.

The CROPS mandate’s “Censorship Resistance” property focuses on inclusion (can all valid transactions eventually be included?). SE-MEV reveals a second dimension: ordering neutrality — does the protocol ensure no party can systematically win ordering races purely by paying for priority?

Key Sources

  • Ordering Power is Sanctioning Power: Sanction Evasion-MEV and the Limits of On-Chain Enforcement (Wu, Bai, Ren, Zhang, Cao, Wang, Wen, Liu — Zhejiang University / HKUST-GZ, Mar 2026) — First sanctions dataset; SE-MEV definition; game-theoretic model; arms race trajectory