A shifter includes an actuator incorporating a shape memory alloy wire to control movement of lever-position-controlling components of a vehicle transmission shift lever. In one arrangement, the actuator controls movement of a cam to prevent moving a pawl out of park position until predetermined vehicle conditions are met. Alternatively, the actuator can be directly attached to the pawl itself for controlling movement of the pawl, or connected to a toggle linkage arrangement for controlling movement of the pawl. In still another arrangement, a magnet arrangement is used to motivate a pawl-blocking member. When necessary, a mechanical fuse is operably connected to the system to prevent damage to the shape memory alloy wire where there is risk of the pawl being frictionally stopped from movement despite the contraction of the shape memory alloy wire actuator.