[Avodah] Just what ARE the rules of p'sak anyway?

[Chana Luntz]

RYG writes:

> --- Begin Quote ---
> 
> [Quoting the T'rumas Ha'deshen:] But in the [aftermath of 
> the] decree of Austreich they [women who had been captured by 
> gentiles - see the previous section of the DM] were 
> permitted, on the authority of Gedolim, to their husbands 
> too, even to Kohanim ...
> 
> [The DM himself:] And it seems to me that perhaps the Gedolim 
> who permitted did not do so Mi'dina but for a Zorech Sha'ah, 
> for they saw that we must be concerned for future women, that 
> if they were to know that they would be unable to return to 
> the husbands of their youth, they might sin, and so they were lenient.
> 
> And do not say, can we be lenient with regard to an Issur 
> De'oraisa? It seems to me that they relied on that which it 
> is stated "kol d'me'kadesh a'da'ata d'rabbanan m'kadesh" and 
> Beis Din has the authority to nullify their Kiddushin and 
> they are therefore as single women and even if they have 
> strayed they are permitted to their husbands, so it appears to me.
> 
> --- End Quote ---
> 

I must be missing something here:

A) why did they not rely on the more usual their zera is considered like
susim? (I always thought, despite the unhappiness of the Sridei Aish
about this idea, that it was precisely for these reasons, and because
this sort of thing happened too often, that it was good we held this
way);

B) How would afkinu help for Cohanim anyway, whether she was considered
married to her husband the Cohen at the time or not, the problem of
zonah would surely still exist?

> Yitzhak

Regards

Chana