CA SB139

Requires counties with more than 400,000 residents to establish a 9-member or 12-member independent redistricting commission by March 1, 2021, and every subsequent year ending in "1" to adopt supervisorial districts after each federal decennial census.

Counties that fail to pass an ordinance establishing a commission by March 1, 2020, and subsequent years ending in "0" must establish a 12-member commission by default.

Establishes two alternative commission formation procedures (Sections 23005 and 23006): Section 23005 creates 12-member commissions with proportional political party representation; Section 23006 creates 9-member commissions with equal representation from the two largest parties and other voters.

Requires commissions to hold at least five public hearings with at least one in each supervisorial district, provide live translation in applicable languages, and publish draft maps for public review at least seven days before adoption.

Allows the board of supervisors to petition superior court for an order establishing supervisorial boundaries if the commission fails to adopt boundaries by deadline, and exempts Los Angeles and San Diego Counties unless their existing redistricting laws are invalidated by court.