A shifter includes an actuator, such as a shape memory alloy wire, to control movement of a set of strategically placed magnets on lever-position-controlling components of a vehicle transmission shift lever. In one arrangement, the actuator controls movement of a carrier carrying one or more of the magnets, the magnets controlling a position of a blocking member to prevent moving a pawl out of park position until predetermined vehicle conditions are met. Alternatively, the magnets can be carried by a cam, or slide, or wheel.