When reading "Who Dares Wins" by Tony Geragthy, he described SAS operations against known IRA militants,if they had the position of a IRA weapons catch, they(SAS soldiers) would stake out the location and if they had a confirmed IRA member approaching the catch, they were only allowed to engage them if they picked up the weapon and showed hostile intent. Was this a general order for British soldiers in Northern Ireland or was the ROE more restrictive for soldiers that were not special forces?
I'm not familiar with the book but it sounds very much like he is describing specific special forces actions rather than a general order, simply because of the way weapons related to the troubles have been and still are discovered and dealt with since they began - although note that many british press reports on troubles cache finds (such as thisone )give mention that the old 'dog walker found it' story is probably very convenient in such cases.
Standard operating procudre for both British and Irish govt's during the later troubles was to have their Armies both publicly there to step in as a reactionary force and to dispose of found weapons/explosives, but to leave the day to day investigation of dissidents to the relevant police force. Of course, in 1976 the British govt were forced to admit that they had been operating special forces inside Ireland.
Although don't take this to mean the British forces had the situation on lockdown, far from it. There were several different actors on military/law/parmilitary sides so a lot of small weapons caches which remained untouched, maybe even still in situ today. Staking them out as standard simply would not be a worthwhile exercise, not without damn good intel that the right men were to be there. It's well worth noting that a 2004 report brought to light the actions of Garda officers setting up hoax cache finds and border runs simply to gain kudos from their superiors and the Northern security forces.
http://mikeb302000.blogspot.co.uk/2011/12/rules-of-engagement.html
These flash cards show the rules of engagement in Northern Ireland during the Troubles. They aren't too dissimilar to what was employed in Afghanistan, I assume.