PA-30 pilot reported losing control of the aircraft during the landing roll-out while the student pilot attempted to free the shoe that got stuck in the rudder/brake pedal. A runway excursion occurred and the aircraft's propeller struck a light.

Narrative

During the ground roll braking after a successful southeast landing; the student pilot's foot / shoe became lodged in the right rudder / brake pedal assembly. While attempting to dislodge his right shoe from the rudder / brake pedal via negative back pressure; the left pedal was either inadvertently pressed or forced forward due to negative back pressure on the right pedal. This left pedal drive forced the airplane to veer off the left side of Runway XX onto Taxiway XX. The veer increased and caused the airplane to spin 180 degrees off the south side of the taxiway into the gravel. Upon crossing the taxiway on to the gravel; the right prop struck a taxiway / runway light; destroying the light and minorly damaging the prop. Lesson learned. Identify stuck controls as early as possible. Ensure both sets of rudder pedals have braking capability. Ensure all pilots are familiar with potential control interferences or catches. Never force braking. If a pilot notices something is stuck; maintain runway alignment and roll out as far as needed.