You can debate all day whether you want to let them fight it out instead of using the rules, but if you want to follow the rules, it seems an obvious lane impedance, which is specifically covered in the rules as "shall be disqualified"
Lane Infringement, 4(b)
An athlete shall not be disqualified if he steps or runs outside his lane in the straight, any part of the diversion from the track for the steeplechase water jump or outside the outer line of his lane on the bend,
* with no material advantage thereby being gained and no athlete being josteld or obstructed so as to impede his progress. If material advantage is gained, the athelete shall be disqualified.