The FDA has given the Lightsheer^®  approval for permanency.

LightSheer^® gets further FDA approval

Coherent, Inc. (Santa Clara, CA) (NASDAQ:COHR) announced (April 19, 1999) that the LightSheer Diode Laser System received clearance from the U.S. Food & Drug Administration to claim that it achieves "permanent hair reduction." This is the first such clearance to be granted to the new generation of diode laser technology. 

In layman's language:
Both electrolysis and the LightSheer^® offer permanent hair removal, or more correctly, hair reduction.

Hair follicles go through cycles of growth, decay, and rest. Only hair in active growth phase can be treated.

During any treatment (laser or electrolysis) session, a number of follicles are destroyed permanently. But the hair in rest phase, and hence not visible at the time of the session, are not destroyed. These will start to grow at the end of their rest phase.

The net result is that the number of hair in the treatment area has been reduced and the reduction is permanent.

Subsequent treatments will reduce the remaining hair in the area even further. The number of treatment sessions required to remove all unwanted hair in an area varies from person to person.