There is no enable/disable action through events for the shadowlight itself.
It is not even an available property for it either.
You can play with the opacity of it though.
At opacity 0, objects with shadowcaster behavior will not display a shadow.
Although, it may be easier to answer your question seeing your exact project.
Consider making a reproduction of your dark room and torch sprite and post it.
This worked perfectly for my current scenario, thanks!