I did some experimenting and discovered at least a partial answer to my question. If you select Law for your squad when beginning a mission, then even if she transforms into Order, he won't jump. But if you start with Order on your squad, then both he *and* Law have the ability to leap tall buildings with a single bound.
It's a bit of a pain, because it makes it harder to level the two of them up at the same rate (since whichever one of the pair you actually select for the squad will receive more XP for the mission). I'm hoping that once Law gains a level, the problem will go away (she has 500 XP currently, to Order's 600), but it remains to be seen. I'd still like to know if anybody has an actual fix for this bug.