Laser jamming is legal (as far as I know), radar jamming is illegal.
Edit- My bad, they are both illegal but there are some really cool kits out there but if you have a quality radar detector and don't normally drive 100MPH you should have enough time to slow down before you get clocked (this is ofcourse unless they get you with a laser gun, if they do you are snagged if you where speeding cause this wouldn't go off til they actually clocked you)
Edit 2- Actually after reading this, it states that radar and laser jammers are legal in this state so I am not sure
http://www.radarbusters.com/legalissuesarticle.cfm
"Laser Jammers and Radar Jammers are illegal in the states of Nebraska, Minnesota, Utah, California, Oklahoma, Virginia, Colorado, Illinois and Washington DC. "