it looks like the bush administration is determined to render the designation "terrorist" completely meaningless. it used to be that a "terrorist" was a non-soldier who intentionally used violence against civilians or civilian targets to further a political or military goal. the military of a state was excluded from the definition. intentionally attacking civilians by a military force was a war crime, but it wasn't terrorism.
then years ago, the bush administration started calling attacks on the u.s. military (or the military of its allies) "terrorists attacks" even though they weren't directed against civilians. that way, they could count any ambush or sniper attack on u.s. forces in iraq as "terrorism" even though under in any other war it would simply be called "military combat." the new "terrorism" eliminated the "civilian target" element of the definition, but still seemed to require that the attacks were conducted by groups that were not the military of any government.
but by calling the revolutionary guard corps, a branch of the iranian military, a terrorist group, they're crossing yet another rubicon. not only can people attacking military targets qualify as "terrorists", but also the people attacking can themselves be military.
but this creates a host of problems. there was a reason for the military exclusion--it avoided a whole lot of stuff that we don't want to be called "terrorism" from being called "terrorism." like, for example, actions taken by the u.s. military. by bush's logic, the bombing of dresden would be a terrorist attack. as would the bombings of hiroshima and nagasaki. since both military actors and targets now can be part of a terrorist attack, it seems that every attack ever carried out by the u.s. would be "terrorism." indeed, by that logic any violence in the world qualifies as a terrorist attack.
there really is no stopping point. the word "terrorist" has always been open to political manipulation. iraq, for example, was added to the state department's list of state supporters of terrorism in late 1990, not because it had just been linked to any particular terrorist attack, but rather because the u.s. was trying to build a coalition against the iraq government on the eve of the gulf war. but the bush administration's extension of the term goes way beyond that. now it can include just about anything, which effectively renders the term "terrorism" meaningless.
and yeah, i think this is nothing more than a clumsy effort to create a legal justification for attacking iran. as usual, the bush administration doesn't seem to notice all the ramifications of its actions. by distorting the word "terrorism" this much, the administration is also building an argument that the u.s. is a terrorist state.