There are, in my view, some basic differences between a terrorist and an insurgent. As mentioned before, to my way of thinking the first of these is geography. I also view both terms as neutral in the great scheme of things. There can, from some perspectives, be “good” terrorists and “bad” insurgents, as well as the reverse.

I don't deny the impact of “global community” thought with this, but the relationship between “struggle with authority” (however that may be defined) and a group based on a particular tribe or local issue is to me at the heart of an insurgency. Once it begins leaving local borders, and takes on the trappings of the “global community,” it may well cross into a trans-national insurgency or terrorism. To be more precise, it may become a trans-national insurgent group or terrorist group. I make a distinction between terrorist tactics and methods (terrorism) and groups that practice terrorism.

The base of a typical insurgency remains geographic. While they may solicit outside support and assistance, their goals remain reasonably local (nationalized land holdings, revoking nationalized land holdings, correction of perceived or real social wrongs, and so on). If outsiders can help attain those goals, or distract the local “powers that be,” an insurgent group will use them. I would also argue that while some insurgent groups may have a loose command and control network (although this is not always the case), they still feel responsible to a fixed goal or vision. This is also something that can be easily measured (like the goals mentioned before). Tribal insurgencies, as Stan points out, may have issues getting off the ground, but each tribe remains fairly fixed in its goals and objectives. By this measure, groups like ETA may actually straddle the fence between terrorists and insurgents.

This geographic focus also places, to my view, some limits on the methods an insurgency can employ. These limits are determined more by their base constituency or recruiting pool, and not so much by outside considerations. For example, an insurgency would lose momentum if it continually committed atrocities against its own core population (this is, of course, assuming that the insurgency is not being controlled by others and used for their own ends...my thought here is the Viet Cong by about 1965, although the transition could have taken place earlier). Once they take that step, they become more committed to terrorist methods and the basic profile changes.

Terrorists, on the other hand, have goals and objectives that cannot be easily measured or attained (bringing Ireland under a Socialist/Marxist/whatever government, for example). For them geography is a consideration but not a focus. Also, these groups tend to spin out of control over time, becoming much more hazy in their goals and more violent in their methods. They become, in short, addicted to the killing (their own methods) and less focused on what those methods are supposed to achieve. Some insurgencies (like the ETA, the Khmer Rouge, and others) transition into terrorist groups as their goals become less clear and their methods more violent and less focused.

To me, a trans-national insurgency runs the very real risk of becoming a terrorist group because they lose that geographic focus. One of the first signs of a terrorist group spinning out of control is the conversion to a more hazy political or socio-political goal. “Global Community”-type insurgencies would be especially vulnerable to this, as their leadership would be dispersed and more open to influence by more radical (or extremist) elements. And once they start shedding their self-imposed limits, they run the real risk of falling into the classic terrorist spiral of violence.

Just some slightly more organized thoughts...