The IJF does a pretty good job at being specific down to the minute detail of every possible case in defining the rules of olympic judo. There has been a bunch of changes in the rules in the last several years, specifically the addition of a “dynamic edge”. The rules relevant to this are defined on page 12 of this 2009 Judo Refereeing Rules. Basically any attack that starts inbounds but continues out is still valid. What’s important is that this only applies to tachi-waza (the standing part of judo) and not to newaza (the on the ground part).
In newaza, you’re inbounds as long as some part of your body or your opponent’s body is in contact with the contest area. In the video below, the commentator says otherwise. What happens is this:
- White applies an armbar
- Blue rolls to his back
- The ref believes both to be out of bounds and calls “matte” (stop)
- Important: Blue did not tap
- The refs change their mind and give White the win.
The rules are pretty clear about there having to be contact with the mat in order for you to be counted as inbounds, so I believe White was out of bounds, but it’s a close call and certainly arguable either way.