UPDATE:


I detailed my car a while ago and finally got to pull out the headlight to get rid of the humidity - it recondensed two days later.

I considered pulling the housing apart by heating it like senor said but I've never seen good results with anything other than the original glue to reseal it so I took a little bit more innovative of an approach.

I rinsed it out, then I filled it with rice and left it there for 30 minutes then I dumped it out and put about a tsp more in and closed it up. Three weeks later the condensation hasn't returned!

As soon as I make a trip to work im gonna pick up some silica packets and pour a little of that in each side - its clear so it should blend in better!

Cliffnotes:
Poor a little silica in and forget about resealing it.