[Avodah] shabbas//mishum eiva, etc???

[Harvey Benton]

could someone please explain to me the process of how and why and when
the chachamim are allowed to enact, or go around, clear midoraisa guidelines???
eg, mishum eiva saving an aino""yehudi, etc, {or is that not a midoraisa???}; 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.aishdas.org/pipermail/avodah-aishdas.org/attachments/20110807/99ec21dc/attachment.htm>