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+---
+arc: 1644
+title: Controller Operations for Security Tokens
+description: Forced transfer and redemption controller interface for regulated tokens
+author: Ludovit Scholtz (@scholtz)
+discussions-to: https://github.com/algorandfoundation/ARCs/discussions
+status: Draft
+type: Standards Track
+category: Interface
+sub-category: Application
+created: 2025-09-03
+requires: 88, 200
+replaces:
+---
+
+# ARC-1644: Controller Operations for Security Tokens
+
+## Abstract
+
+ARC-1644 defines standardized controller powers for security tokens on Algorand, enabling forced transfers and redemptions under strictly governed conditions (e.g., court order, regulatory action, error remediation). It mirrors Ethereum's ERC-1644 while adapting privilege enforcement to Algorand's ARC-200 token control and smart contract mechanism.
+
+## Motivation
+
+Certain regulated events necessitate administrative intervention. A predictable, auditable interface reduces systemic risk and ensures interoperability across custodians and secondary trading platforms.
+
+## Specification
+
+### Controller Authorization
+
+Global state MUST store `controller` (address) OR a list of controllers in a box `controllers`. A multi-sig or logic signature is RECOMMENDED. Changes to controller set SHOULD be timelocked via `pending-controller` + `activate-round` pattern.
+
+### Required Methods (snake_case, ARC-4 types)
+
+Canonical ERC-1644 defines 3 functions: `controllerTransfer`, `controllerRedeem`, `isControllable`. Base ARC-1644 mirrors that minimal surface; controller management is an extension (see 3.4).
+
+All base methods are namespaced with `arc1644_`.
+
+- `arc1644_controller_transfer(from: address, to: address, amount: uint64, data: bytes, operator_data: bytes) -> (code: uint64)`
+  - Forces a transfer of `amount` from `from` to `to`.
+  - MUST return a status / reason code consistent with ARC-1594.
+- `arc1644_controller_redeem(from: address, amount: uint64, operator_data: bytes) -> (code: uint64)`
+  - Forces redemption (burn) from `from`.
+- `arc1644_is_controllable() -> (flag: uint64)`
+  - Returns 1 iff controller operations are currently enabled.
+
+Partition awareness is intentionally NOT in the base interface (matches ERC-1644). A Partition Controller Extension is defined in section 3.5.
+
+### Semantics (Base)
+
+Controller operations bypass standard sender consent but MUST still respect partition invariants and reason codes. Forced actions SHOULD emit logs referencing `operator_data` justification.
+
+### Controller Governance Extension (Optional)
+
+If an implementation wishes to expose on-chain controller set governance, it MAY add:
+
+- `arc1644_set_controller(new_controller: address)` (timelocked commit pattern RECOMMENDED)
+- Or multi-controller form:
+  - `arc1644_add_controller(addr: address)`
+  - `arc1644_remove_controller(addr: address)`
+
+Timelock pattern: store `pending_controller`, `pending_set_round`, enforce activation after `pending_set_round + min_delay`.
+
+Disabling control: A governance call MAY irreversibly set `controllable = 0` and zero out controller address(es); afterwards `arc1644_is_controllable` MUST return 0 permanently.
+
+### Partition Controller Extension (Optional)
+
+For tokens implementing ARC-1410 partitions, the following extension functions MAY be added (mirroring ARC-1410 semantics):
+
+- `arc1644_controller_transfer_partition(from: address, to: address, partition: bytes32, amount: uint64, data: bytes, operator_data: bytes) -> (code: uint64)`
+- `arc1644_controller_redeem_partition(from: address, partition: bytes32, amount: uint64, operator_data: bytes) -> (code: uint64)`
+
+Reason code mapping MUST remain consistent with ARC-1594; partition not found or insufficient balance codes SHOULD reuse existing insufficiency codes.
+
+If extension is absent, attempts to call these methods MUST reject.
+
+### Semantics (Partition Extension)
+
+Controller partition operations bypass holder consent but MUST maintain partition accounting invariants identical to standard partition transfers/redemptions.
+
+### Execution Pattern
+
+Implementation configures ARC-200 transfer authority such that only application-governed logic can perform forced movements (e.g., via a logic-controlled clawback equivalent or authority address). `arc1644_controller_transfer` constructs an inner ARC-200 transfer `from -> to`. If using an external authority address, ensure it is rekeyed / restricted to contract governance.
+
+### Events (Logs)
+
+Base (no partition):
+
+- Tag 0x31 arc1644_controller_transfer | controller | from | to | amount | code
+- Tag 0x32 arc1644_controller_redeem | controller | from | amount | code
+- Tag 0x33 arc1644_controller_changed | old | new
+
+Partition Extension (if implemented):
+
+- Tag 0x34 arc1644_controller_transfer_partition | controller | from | to | partition | amount | code
+- Tag 0x35 arc1644_controller_redeem_partition | controller | from | partition | amount | code
+
+### Reason Codes
+
+Implementations MUST reuse ARC-1594 codes. Recommended additional (extension) codes if not already allocated:
+
+- `50` ControllerUnauthorized (caller not an authorized controller)
+- `51` ControllerDisabled (controllable flag off)
+- `52` JustificationRequired (non-empty operator_data required)
+
+These codes SHOULD NOT collide with existing ARC-1594 numeric assignments; if conflicts arise, implementers MAY shift into an unused high range (e.g., >= 200) but MUST document mapping.
+
+### Safeguards
+
+- Mandatory justification: if global `require-just` == 1, `operator_data` MUST contain a non-empty explanation or legal reference identifier.
+- Rate limiting (optional): store last controller action round; enforce minimum interval.
+- Audit trail: append structured log with reason code + hashed justification docs.
+
+### Disabling Control
+
+`arc1644_is_controllable` may return 0 after a governance decision to renounce override powers. Implementation sets `controller` to zero-address and `controllable` = 0 (immutable).
+
+## Security Considerations
+
+- Ensure controller cannot mint (that's issuance) unless explicitly allowed; separation of duties.
+- Timelock controller changes to mitigate key compromise.
+- Make justification transparent while avoiding sensitive full-text storage (hash large documents).
+
+## Backwards Compatibility
+
+If not implemented, `arc1644_is_controllable` MUST return 0 and controller methods MUST revert / reject with `51`.
+
+## Reference Implementation
+
+[arc1644.algo.ts](https://github.com/scholtz/arc-1400/blob/main/projects/arc-1400/smart_contracts/security_token/arc1644.algo.ts)
+
+## Rationale
+
+Partition-neutral base mirrors Ethereum minimalism; extension keeps core lightweight while enabling regulated partition operations when ARC-1410 present.
+
+## Copyright
+
+CC0 1.0 Universal.