I've been in Aikido a long time, but I've certainly never heard of anything like an "Aikido martial law protocol". People get challenged for the leadership of groups all the time - I've seen it in dojos in the US, and I've seen it in dojos in Japan, there's not much difference.
I've been aware of an "enforcer". One (late) shihan would send one of his higher ranking students/uchideshi to dojo where either a sensei or a higher up student wasn't doing things "right". AIUI the "enforcer" would spend a little time "practicing with" the person who was being a problem. There may also have been some discussion, but (and this is all hear-say) the problems would usually resolve.