AB 2663 will modify the California tax code to allow property transfers from domestic partnerships to be reassessed back and effectively reverse the change in tax base. Reassessment between the years 2000 and June 26 2015 as a result of a domestic partnership can be reversed if filed before June 30 2022.
This is significant, tax-wise, due to proposition 13 affect on property taxes. In California, a property will not be reassessed for tax purposes unless it is sold (and some other smaller occasions). The California tax code allows some family transfer to be exempt from the tax, and now domestic partnership is also included in that.
More importantly, domestic partnership is a legal status that many gay and lesbian couples used in lieu of marriage. The US Supreme Court ruled in 2015 that same sex couples have a right to marry, reversing the California constitutional amendment, Proposition 8 that defined marriage between a man and a woman.
You can read the full text of the new law here.
The Governor signed AB 2663 into law on September 29, 2018.