Headlight covers are illegal at anytime, anywhere, at any officer's discretion. They are meant for offroad use ONLY. Says right on the box. TECHNICALLY, an officer could pull you over the second you roll out onto the pavement. But anytime from dusk and forward you're just stupid (no offense) to have them on. A) Because you WILL get pulled over for it B) You can't see CRAP with them on compared to having them off.
I had them for a few months, I was hooked on them for whatever reason, then came to my senses and just threw them out. They're a real pain in the ass to be quite honest, crack frequently especially during the winter, and are far overpriced...
So if its dark, even dusk, raining, or anything that requires your headlights to be on, you can't have the headlight covers on.
I also got a ticket in NJ for headlight covers, Rob. It was nice and sunny and about 75 degrees. You might be familiar with Winslow, near Cranbury (where I used to work). Those cops are the biggest fartknockers around. They used to sit right at the exit offramp of the Turnpike and just pull people over left and right. I only went off that exit twice and got pulled over both times. Never went there again and never had a problem after that.
They are illegal no matter what time of the day and weather conditions. They are meant for off-road use ONLY. But many cops don't realize that. Bottomline though if you have them on at any time when it's dark out you're a freaking idiot because you can't see anything with them on, and you are just asking to get pulled over and get a ticket.