Glad I brushed up on Algeria since it features so prominently in recent Malian events. I still have a lot to learn, though!
Although Algeria's constitution forbids its forces from taking part in military action outside its own territory, the constitution, in practice, is used more as a pretext to justify not sending its military outside its borders. For instance, it is this aspect of the constitution that Algeria has been continually invoking over the last couple of years to explain why its forces have not crossed into Mali to obliterate AQIM, even when invited to do so by its Sahelian neighbours (Niger, Mali and Mauritania), with whom it set up a joint military command in April 2010 for precisely this purpose.
The reason why Algerian forces have hitherto desisted from going into Mali to root out AQIM cannot therefore be because of the constitution. The real reason is that the AQIM in the Sahara-Sahel is a predominantly Algerian construct. source
The series of terrorist groups, or names of various terrorist groups, in the north of Mali is dizzying. Sounds like a tricky path ahead for Algerian/US relations if Algeria is backing (and/or is?) AQIM and the US is engaging in counterterrorism.... Tricky pickle much?