thanks Vim!
yes AFAIK the four countries i mentioned up-thread have tended to be involved in the most enemy contact out of international forces (or i think did the last time i was following this with any regularity which i admit was way back last summer; also Denmark has had the most troops killed of any international country relative to population).
this is mostly because their troops, especially Canada, the US and the UK, have been deployed in what have been the most dangerous areas, and less, i think, to do with their rules of engagement being significantly different from that of other partners.
i don't think the British ROE are much less strict than the German ones, say.
what can differ considerably from country to country is the caveats.
Much has been made by various commentators in recent months about the negative impact national caveats are having on Nato/ISAF operational capabilities in Afghanistan. As well as affecting operational effectiveness, such caveats - which place self-imposed restrictions on the way in which individual national forces may be deployed - are having a corrosive effect on relations between contributing Nato countries, and on overall ISAF morale.
Although forces from all 26 Nato member states are deployed in Afghanistan, only Britain, America, Canada, Denmark and Holland have not used caveats to limit the rules of engagement of their troops.
article from May 2008
here, idk about current accuracy, but these caveats must be pretty dispiriting for some ISAF top brass