[Avodah] Ein Mevatlin issur lechatchilah

[Micha Berger]

On Mon, Mar 09, 2009 at 03:00:24PM +0200, Eli Turkel wrote:
: RMF has a teshuva allowing ice cream even though it contains small
: amounts of Gelatin which might be davar hamamid.
: Thus, it was obvious to RMF that once it is batel by the company
: one can buy it lechatchila and give a hechsher,

Is there any case where bitul can be undone? (And we perhaps need to
delve into rov as birur vs batul berov.)

E.g. erev Pesach, bitul because of a gezeira is strong enough to
continue even after issur chameitz de'oraisa is in effect!

Tir'u baTov!
-Micha