Every motion light starts with a conventional light fixture and adds the motion and light sensor. A competent electrician can safely disconnect the controls and the result will be just a regular fixture.

Busdriver mentions added controls for the sensor.... when it comes down to it though, (ideally) there should only be 3 wires controling the fixture (hot,neutral,ground)and not an extra hot etc for the sensing controls. Just saying in case I just want to swap out the old fixture.

Still want to say there a standard trick to use it manually besides bypassing the controls. Like quickly turning the switch on and off in the right configuration.

Some of the newer, more sophisticated controls might have a means of override similar. If you can get some sort of number off of the control or fixture and do a search you might hit the jackpot.