Electronic lock, intended to be controlled by a key having electronic means for controlling the unlocking of the lock, the lock including: - a stator and a rotor that is mounted so as to rotate in the stator and equipped with a channel into which the key is able to be inserted, - an element for blocking the rotor, able to move in a recess in the stator between a blocking position in which it engages with the rotor so as to block rotation of the latter and a retracted position in which it frees up the rotation of the rotor, - a mobile stop able to move, in response to an electric unlocking command, between a first position in which the mobile stop is able to be trapped by the blocking element so as to oppose movement thereof from its blocking position and a second position in which the blocking element is free to leave its blocking position, - a return arm able to move, even if the mobile stop is trapped by the blocking element, in response to the electric unlocking command, between: • a rest position in which the mobile stop is not driven into its second position, and • a return position in which the mobile stop is driven into its second position by a return means, - the return means, and - an immobilization mechanism (52, 54) able, without consuming electrical energy, to hold the return arm in its return position even after the electric unlocking command has passed, so as to mechanically store this command, characterized in that this immobilization mechanism comprises a part (52, 54) able to be attracted by a permanent magnet and a permanently magnetized portion (52, 54) able to exert an attractive force on this part that makes it possible, without consuming electrical energy, to hold the return arm in its return position when the magnetized portion and the part are facing one another. - a stator and a rotor that is mounted so as to rotate in the stator and equipped with a channel into which the key is able to be inserted, - an element for blocking the rotor, able to move in a recess in the stator between a blocking position in which it engages with the rotor so as to block rotation of the latter and a retracted position in which it frees up the rotation of the rotor, - a mobile stop able to move, in response to an electric unlocking command, between a first position in which the mobile stop is able to be trapped by the blocking element so as to oppose movement thereof from its blocking position and a second position in which the blocking element is free to leave its blocking position, - a return arm able to move, even if the mobile stop is trapped by the blocking element, in response to the electric unlocking command, between: • a rest position in which the mobile stop is not driven into its second position, and • a return position in which the mobile stop is driven into its second position by a return means, • a rest position in which the mobile stop is not driven into its second position, and • a return position in which the mobile stop is driven into its second position by a return means, - the return means, and - an immobilization mechanism (52, 54) able, without consuming electrical energy, to hold the return arm in its return position even after the electric unlocking command has passed, so as to mechanically store this command, characterized in that this immobilization mechanism comprises a part (52, 54) able to be attracted by a permanent magnet and a permanently magnetized portion (52, 54) able to exert an attractive force on this part that makes it possible, without consuming electrical energy, to hold the return arm in its return position when the magnetized portion and the part are facing one another.