Lining up along the land

[Ref in PA]

A1 at the line shooting 1 free throw. A2 gets in his proper slot, between B1 and B3. A2 then takes 2 steps perpendicularly away from the lane (east/west), still staying within the extended boundaries of the lane slot. At what point does this become a violation? if ever? Does one foot have to be along the lane area? within 3 feet of the lane? I know what my opinion is, but am interested in yours. I have read 9-1-9 and feel the answer may be there, but to me it is not plain.