A holster for a handgun, having at least some of an at least partial cavity; a lever having a thumb button portion and an engagement portion, wherein the lever includes a locking projection extending from at least a portion of the engagement portion, wherein the lever is pivotally attached or coupled to at least a portion of the holster, approximately between the thumb button portion and the engagement portion; and a lockout element, wherein at least a portion of the lockout element is positionable to block movement of the lever to keep the lever from being pivoted to a disengaged position.