Why wouldn't 3,000 lumen halogen lamp be legal?

Google found this for me:

What about higher-wattage bulbs for my DOT-spec headlamps? One word: DON'T! If your headlamps have plastic lenses and/or plastic reflector housings, you mustn't use overwattage bulbs, as this can create serious fire hazards and cause extensive (and expensive) damage to the headlamp assemblies and wiring in short order. Even if your headlamps use glass lenses and metal reflector housings, you still can't safely use these bulbs because the wiring in DOT-spec headlamp systems is not capable of handling the level of current these bulbs will draw. If you disregard this and do it anyhow, you create several serious fire hazards in the engine compartment and, more worrisome, in the passenger compartment at the headlamp switch. This problem could be circumvented with the installation of an extra-heavy-duty relay and heavy wiring, but the wiring is only as robust as its highest-resistance section; the 9004/HB1,

9005/HB3, 9006/HB4, and 9007/HB5 bulbs used in DOT-spec headlamp systems all have extremely small electrical contacts. Go ahead and have a look; they're really spindly! These contacts get extremely hot even under normal (45 to 65 watt) loads. They get dangerously hot under higher (80w, 100w, etc.) loads. When you go much above 65 watts, these contacts become the point of maximum resistance. Things start melting and burning, and due to the voltage drop involved with such resistance, you will not achieve any improvement in your headlamps' ability to light-up the night. No reputable bulb manufacturer makes these overwattage DOT bulbs for that reason. The ones you may find are third-rate junk that not only will not last very long, but also are made in factories with little or no quality control and do not tend to be made to the extremely precise filament-placement specifications demanded by today's advanced headlamp designs for proper lamp performance. Even if you could find (nonexistent) overwattage bulbs in these formats with oversized contacts and ceramic bases, make your wiring adequate to handle the extra load, and be sure your headlamps contain no plastic, you *still* would be wasting your time and money to use the overwattage bulbs, because the optics and beam pattern specified in such headlamps by the DOT does not respond to overwattage bulbs, except to cause massive dazzle to oncoming traffic and drivers in front of you via the rear view mirrors, and to cause extreme backglare in fog, rain or snow. Any way you slice it, overwattage bulbs are a bad deal all around. You'll do well to avoid them.

My guess is focusing.

Unless you can find a reflector assembly that keeps the brightness pattern the same as HID lights (sharply focused so as to produce a sharp line between "bright" and "dim") then such high-power incandescents will simply be too bright for other drivers.

Hmmm, I sure do detect a familiar writing style. Betcha I know what website that came from ;-)

But I think his question related not to the practical limits of halogens (heat, current draw) but why a *hypothetical* halogen source that wouldn't cook reflectors and emitted the same amount of luminous flux as a 3000 lumen HID isn't allowed.

And I think the answer is either a) it IS allowed if the capsule emitting the light can be made to draw less than the required maximum (HIR bulbs, for example emit more luminous flux per watt consumed than regular halogens), or b) its just that the regs limiting wattage were probably written when all lights were similar technologies and watts corresponded more directly to luminous flux.

Given that in most ways halogen light is better and easier to deal with than HID (better color rendering, better alignment with the eye's natural sensitivity, filament shape is more controlled than arc shape so focusing is more precise, etc.) there's no real engineering reason.

But I defer to Dan Stern for anything beyond speculation.