How's it possible that this light is legal?

Why would it not be? Your subject implies there's an STC, which clearly
makes it legal, but even if we're just a victim of a misleading subject,
it
could have been installed as a one-time 337 approval.

I suppose it's possible he got a field approval for (what appear to be)
Subaru fog lights on the struts of a certificated aircraft. It just
doesn't seem to happen that way in my neck of the woods.

Personally, I think it's the greatest landing/taxi light I've seen. The
fact that he had the balls to fly into a major fly-in with those installed
indicates that either:

a) They ARE legal
or
b) He's a ramp check waiting to happen

The thing I'm trying to figure out is, you were at the fly-in yourself,
you
took the picture of the landing lights (it seems), but you didn't ask the
owner of the airplane directly?

We never did run into the guy who owned it. It was just one of over 130
Cherokees, parked wingtip to wingtip. We took pictures of many of them.

Even if the owner weren't around, you could have left a note.
I have been left notes on my own airplane, and am perfectly happy to phone
someone who wants to ask about it.

'Spose we could have. Instead we just took the picture and kept on walking,
laughing.

I really want a set of those $39.95 "landing lights!" They sure expose the
$1K "Boom beam" for the rip-off it really is, and probably work almost as
well. Maybe better, on the ground.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"