A locking assembly is provided to simply and effectively prevent any unintentional adjustment of the adjustable valve mechanism in a fluid flow control device, without compromising the function of the device. The locking assembly generally includes at least one gripping arm for frictionally engaging at least a portion of the adjustable valve mechanism, and an actuating mechanism for controlling the deployment and release of the gripping arm. The locking assembly prevents unintentional adjustments that can adversely affect the pressure settings of the fluid flow control device. In particular, the locking assembly prevents unintentional adjustment, such as may be caused by the presence of a strong external magnetic field. The locking assembly can be easily disengaged, such as through the application or removal of an external mechanical force, to allow a clinician to adjust the pressure settings of the fluid flow control device as necessary.