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[anagogy]

In some sense karma is always involved because it conditions what you desire to experience, but karma doesn't always involve other people, so you could conceivably install a limitation on yourself just for the sake of a desired experience or avenue of development.  

Karma is essentially just distortion seeking undistortion (equilibrium). Since all indviduations are manifestations of distortion from undistorted unity, all actions taken from that perspective are some manifestation of that karma working itself out. Sometimes those actions result in more distortion (more karma), which then must be balanced through yet more experience of a reciprocal nature, but there are many different ways or types of experience that will smooth or cancel out the ripples created.

For example, you might have preincarnatively decided you will not take life in war in this lifetime, thus, events would fall in a protective manner and stop you from getting involved if it ever came push to shove.