The antonyms for "be in commission" would be "be out of commission" or "be non-operative." When something is out of commission, it is not functioning or operating correctly, either temporarily or permanently. The phrase is commonly used to describe broken-down or malfunctioning machines, appliances, or equipment. A car that won't start, a stove that won't heat up, or a computer that won't turn on are all examples of things that are out of commission. Being non-operative can also refer to situations where something cannot be used or accessed, such as a room that is closed off or a website that is down.