... if sub(caller(), sload(owner.slot)) {
mstore(0x00, 0x20) // store offset to where length of revert message is stored
mstore(0x20, 0x13) // store length (19)
mstore(0x40, 0x63616c6c6572206973206e6f74206f776e657200000000000000000000000000) // store...