Locked contract means that there are no access keys allowing the contract code to be re-deployed.

In general case, the code can be re-deployed by:

a transaction with a deploy-code action
the contract itself can implement a function call that will trigger deploy-code action

To re-deploy the code with a transaction, the transaction has to be signed with a full-access key. If there is no such key on the contract, there is no way to re-deploy the code unless there is a dedicated support in the contract code itself, and thus we mark such contracts as locked.

If there is at least one full-access key registered on the contract account, the contract is not locked.

Account: @27ba5b9cfc5270ab297c2833bb5784670c247e6d499e5a6dee90e5539ca928f9