A slogan, originally from Lawrence Lessig’s Code and Other Laws of Cyberspace (1999), picked up by the Ethereum and especially Ethereum Classic communities: smart-contract code, once deployed, is the governing law of the interactions it mediates. Whatever the deployed bytecode does is the correct, binding outcome — no off-chain appeal, no reinterpretation by a court, no fork to undo an unintended result.
The principle was load-bearing in the ETH/ETC split over TheDAO: ETC took “code is law” literally and refused to fork to reverse the exploit; ETH treated the DAO attacker’s outcome as a violation of intent and forked regardless.
House on Rock - LangSec in Ethereum Classic argues that “code is law” only makes moral sense if the meaning of the code is knowable — i.e., if there is an unambiguous executable semantics (KEVM), if languages don’t hide implicit behaviour (Fallback Method, Delegatecall), and if users have the tools (LangSec, verification) to learn what a contract can actually do before they transact with it. Without those, “code is law” means “the winner is whoever reads the bytecode better” — which is a law, but not a legitimate one.