In the Training arena if you worked it out with a trainer he could enforce that you guys were left alone.
However damage is turned off in there. Great place to practice, but not so good for true dueling.
DA can be pretty problematic, being ready to change fields at the drop of a hat, or calling the other side over to deal with the offending player could work.
Squad dueling league does use the DA, mostly with pretty fair results.
Most people if they happen to wander into the wrong spot will do the right thing if approached calmly.