zebra2955 wroteRule 2 -5-art 1 –b A fair ball is a batted ball which: b, contacts fair ground on or beyond an imaginary line between first and third base…
Like others have said, once judged fair, it cannot change to foul.
zebra2955 wroteRule 2-16-art 1 a A foul ball is a batted ball: a which settles on foul territory between home and first base or between home and third base..
This is ruling on a batted ball that has not yet been ruled fair, like in the first quote, above.
zebra2955 wroteBatter hits a ball with back spin which first hits beyond this imaginary line between first and third, spins back and settles in foul territory. By rule you could call it both ways or am I missing something here.
It may be possible to call it both ways, but not legally. The instant a batted ball touches anything or anybody on or over “the imaginary line,” it is legally a fair ball regardless of where it rolls.