What does "legal" mean? OK seems a stupid response, but this question has made bush lawyers out of most of us.

Start with the tyre placard on your JK. What tyre size is on that? If you get pulled by a zealous cop and your tyres don't match, you'll be called in to explain to engineering.

With certification the general theory is your tyres can be +7% (circumference I think) and a 2" lift, as long as you don't change your track width. That way the copper will see your certification when he dials in your plate number. This is often interpreted as 33" tyres and 2" lift is the max legal. With certification. And it kind of matches the various ADRs. Roughly.