My methodology is primarily based upon Beth Yosef and Rema - namely by surveying posqim and coming up with a consensus. R Ovadiah Yosef also employs this at times.
See Sefer HaHinuch 78 on Acharei Rabbim l'Hatot.
Some major exemptions
1. Minhag hamaqom such as insular communities - EG Breuer's or Hassidic
2. Minhag Avot
See Rema Choshen Mishpat 25
Some underlying axioms
Halachah through last Beit Din Hagdol in the Lishkah is axiomatic - equivalent of Halalach L'Moseh miSinai. If they had authored a mishnah it would have become THE authority.
The problem? They didn't and so all Oral Law is an approximation.
See Mishneh Torah Hilchot Mamrim 1:1
Halacha devolves upon
• Tutorial Authority
Such as Master-Apprentice model
• Oral Traditions such as mimetics etc.
Source Professor Agus
There is little legislative authority anymore -
Rather authority is analogous to English Common Law and therefore
Case law sets precedent
I reject "Natural Law"
I also Reject those Maimonidists - NOT Teimanim - who claim one Halacha is correct to the exclusion of others
Teimanim follow Rambam via Minhag Avot. No problem
While Neo-Maimonideans are repeating the R Eleizer Hagadol position of Tannur Achnai, that is they are correct by Divine Fiat in face of acharei Rabbim l'hatot
Catholic Israel IMHO does not legislate so much as it can veto a given p'saq
Illustration RMF in Igrot Moshe prohibited Shabbos clocks except for lamps
AIUI, even RZ Frankel was also saying that Catholic Israel can vote on which Minhaggim to perpetuate and which ones fall into disuse. But not to vote on Core Halachah. I have not yet finalized this.
I agree with my friends Michah Berger and David Willig on several issues
• Halacha allows a range of valid P'saq - that's how Catholic Israel can VOTE for option X over option Y
EG 3 matzos vs. 2 matzos
•. Halachah has rules of thumb not absolutes
•. Halachah flows and meanders like a river. It is not as rigid as a railroad track, nor as amorphous as gaseous air. It has boundaries and it flows. One does not reach back 1000 years are restore a norm from then and ignore subsequent development.
Imagine North American Football devolving back to Rubgy without a forward pass!