Block an Account - Base Documentation

Sometimes you need to stop one address from moving your stablecoin — a compliance hold or a support request. A blocklist denies only the addresses you list and leaves every other holder untouched. Bind it to the sender scope so a blocked account can’t send.

Demo

New to B20? See the B20 Token Standard for the concepts and a full launch walkthrough. These samples target base-std@v1.0.0, viem@2.55.11, and Base Foundry v1.1.1.

Block and verify an account

import { type Address } from "viem";
import { publicClient } from "../../shared/clients.js";
import { POLICY_REGISTRY, policyRegistryAbi } from "../abi.js";
import { sendContract } from "../write.js";

export async function setBlocked(policyId: bigint, holder: Address, blocked: boolean) {
  await sendContract({
    address: POLICY_REGISTRY,
    abi: policyRegistryAbi,
    functionName: "updateBlocklist",
    args: [policyId, blocked, [holder]],
  });
  const authorized = await publicClient.readContract({
    address: POLICY_REGISTRY,
    abi: policyRegistryAbi,
    functionName: "isAuthorized",
    args: [policyId, holder],
  });
  if (authorized === blocked) throw new Error("Unexpected blocklist state");
}

    function setBlocked(uint64 policyId, address holder, bool blocked) public {
        address[] memory accounts = new address[](1);
        accounts[0] = holder;
        StdPrecompiles.POLICY_REGISTRY.updateBlocklist(policyId, blocked, accounts);
        require(StdPrecompiles.POLICY_REGISTRY.isAuthorized(policyId, holder) != blocked, "wrong policy state");
    }

base-cast send "$POLICY_REGISTRY" "updateBlocklist(uint64,bool,address[])" \
  "$BLOCKLIST_ID" true "[$ACCOUNT]" --rpc-url "$RPC_URL" --private-key "$PRIVATE_KEY"
base-cast call "$POLICY_REGISTRY" "isAuthorized(uint64,address)(bool)" \
  "$BLOCKLIST_ID" "$ACCOUNT" --rpc-url "$RPC_URL"

See the complete verified B20 examples for imports, client construction, and runnable projects.

isAuthorized(policyId, account) returns false while the account is blocked.

This only stops outgoing transfers when the blocklist is bound to TRANSFER_SENDER_POLICY. Unblock with the same call and false.

See also

Recover funds · Pause activity
Policy integration in the B20 standard

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