In theory. The majority of manufacturers are building bidirectional charging into new models, already.
The problem with the law, is permitting the government to reverse the energy flow. This is virtue signaling with lazy grid management, instead of investing in reliable energy sources like nuclear. EV's will be treated no different than any other grid connected renewable energy source. This will not be just for your house and in the event of an outage, the energy stored could be moved to a completely different area of California.
California consumes 259.5 TWh and currently only has 5600 MW of battery storage built. That is 0.002% of energy backup.
California had 903,620 light duty EV's registered in 2022. The average EV battery capacity is 40 kWh. That translates to approximately 36144.8 MWh capacity. That's only another 0.014% of backup.
Grid-Connected Renewable Energy Systems.
Alternative Fuels Data Center: Maps and Data - Electric Vehicle Registrations by State.