there is no 'thou shalt not interfere' rule...that's why carter could do her bit for woman's lib in emancipation, they could destroy the 'demon' in demons, and generally stick thier noses in on a case by case basis...take beneath the surface for example...sure by the end they've freed the workers, but now how is the planet going to survive? they destroyed the hammer to free teal'c in thor's hammer then actually had to fix the consequences of their actions in thor's chariot. same wtih double jeopardy...maybe that's what makes it so interesting, their actions are governed by their consciences not a rule...