He meant laser alerts, not laser jammers. Laser alert just tells you you've been zapped, laser jammer alerts you and jams the signal so they can't get a reading.
As Andy (and marriedblonde) says, detection on its own is useless - Laser speed measurement systems give a reading on the gun instantly (well, as close to that as it gets) as the beam hits your car. In short, by the time the detector in your car has sent a beep to its speaker, the gun has some numbers on its display; so you've no time to adjust your speed.
The difference with a jammer is that while it's generating an alert to you that it's reacted to a laser, the gun typically gets 'Error' or its display, as opposed to some numbers which might land you in hot water. Then the jammer goes to sleep after giving you a few seconds to scrub-off some speed, and if the gun operator chooses to zap you again, he will get a reading.
The legality of them is questionable - I still don't think they've actually been made illegal; I think there were some test cases being done with odd charges like attempting to pervert the court of justice or some other thing like that, don't know what the outcome was though...
Anyway, as was said above, even if you get around the laser problem, there's no beating VASCAR - apart from perhaps using the more basic method - not exceeding the limit by too much...
Regards,
Rob.