Over here they are illegal because most people install them on non projector housings. All DOT approved projectors cut at a certain angle and point. Not only that they always cut lower on the driver side so people from the other lane facing you don't get blinded by HID's. On the other had Ricers and others are installing them on Halogen housings that don't cut the light practically blinding anyone they are facing. I got stopped many times with my HID on my four banger and ended up wining all 4 in court when I stated the actual law and that even if my HID's where aftermarket they where DOT approved with number and presented an image of the light being cut after a certain point. Most cops here know they are illegal but dont really know why they are illegal in the first place they just give you a ticket in their ignorance.
Attached is a image of how a DOT approved Projector housing cuts the light output at a certain point and the driver side being lower as stated.
2013 Mustang V6 // Black // 3.31 // Performance Package
Mods: Leather Take-off, GT Brakes Take-off, Borla-S Axel-back