Are they illegal to have?
thats kinda iffy or a gray area.... depends on the officer or who ever you encounter, as with any aftermarket lightening it can be considered a distraction to other drivers if its viewable outside the vehicle...youd have to check your state and local laws...for instance here ins SC anything red blue and/or flashing is iilegal anywhere onthe vehicle...
its one of those things that common sense comes into play, chances are if your not speeding or doing something else stupid or jamming out full tilt around a cop you arent going to get pulled over or cited for it.
I have never had any issues at all with them where they are at and have been since installed, most of the ones made are either red or blue, if its to bring do like someone else suggested and put some tint over it to dim it some, you could even use a relay and attach it to the dimmer switch for your dash lights, or even techforce makes these...http://techforcepcservices.com/shop/viewitem.php?productid=569