There is actually an item for this: Ironmorph dust.
"This bag of powder has a sharp metallic odor. Ironmorph dust can be applied to a willing adjacent creature as a standard action, or thrown as a ranged touch attack with a range increment of 10 feet. On contact, it causes the target’s clothing to stiffen and harden (Reflex DC 15 negates). If the target is wearing light or no armor, his clothing is treated as chainmail for all purposes—including armor bonus, arcane spell failure chance, and armor check penalty—except weight. Exceptionally light clothing (such as a nightshirt or silks) is instead treated as a chain shirt. Exceptionally heavy clothing (such as a cold-weather outfit or elaborate ceremonial garb) is instead treated as full plate. If the target is already wearing medium or heavy armor, he instead gains DR 5/adamantine, but the maximum Dexterity bonus of his armor decreases by 3 (to a minimum of +0), and its armor check penalty increases by 3.
After 5 rounds, affected clothing returns to normal. Ironmorph dust has no effect on creatures not wearing clothing or armor.
Armor or clothing affected by ironmorph dust is effectively metal, and counts as such for abilities or classes that are restricted to certain types of armor (such as druids); however, any abilities that are suppressed or lost due to the ironmorph dust’s effects are restored at the end of the dust’s duration, instead of after their normal time limit."
And it is only 500 gold!
This supports the "Faraday cage" theory mentioned earlier. One could houserule this to also apply to forced wearing of armor (power is cancelled only as long as you wear it).
