Security tag includes a housing and a movable locking element. A latch within the housing is resiliently biased toward the movable locking element and movable responsive to a magnetic field between a locked position and an unlocked position. A guide structure is arranged to constrain movement of the latch. The latch and the guide structure are cooperatively arranged to ensure an engagement that will disrupt a motion trajectory of the latch occurring when the housing is subjected to a physical impact. Consequently, the latch is selectively inhibited from moving fully from the locked position to the unlocked position when the housing is subjected to the physical impact.