Quote Originally Posted by slgrieb
..redesign their wireless LAN equipment because of excessive power output...
This is what limits it commercially, I suppose you could run around setting up points every couple of hundred metres or so, but that's gonna be expensive .. the regulations on this differ by country.

Working out how to measure this though, is hard enough ! check this [pdf] out if you want something to wade through ..

Found this whilst googling as well, which doesn't answer it either ! but does talk about the kind of things you seem to be looking at.

I think this does answer it !

Maximum Output Power, Geographic Location, Compliance Document

1000 mW.........................USA.................... ....FCC 15.247
100 mW (EIRP).................EUROPE ..................ETS 300-328
10 mW/MHz.....................JAPAN..................... MPT ordinance 79