:::::Honestly, I find this position to be a little strange. How is Al-Shabaab and Al-Qaeda not a "militarised force whose function and organization are similar to those of a professional military"? Militaries certainly attack civilian targets (including shopping malls) and shoot people. You twice mention a woman who lived 1400 years ago (honestly, I'm not sure who you are talking about), but my opinion is that this is irrelevant. They have an expressed ideological purpose (terrorism, by definition, does). I think your definition of a summary execution (that it is a punishment for a crime) leaves something out... a summary execution is an execution carried out for a supposed crime, and for people who belong to Al-Shabaab, not being Muslim is a crime. It's a ludicrous position, of course, but nevertheless, murder leaves out the political context, while execution (and other things like assassination) imply a political context, and this context is needed  here. To say that they murdered these people implies that they did so without reason (however crazy we might judge that reason). This is my opinion.