My question involves labor and employment law for the state of: California

I worked for a Silicon Valley firm for four years. During three of those years it was common practice to receive a bonus after completing a major project, and not tied to annual reviews. During the years 2013 through 2015, I received bonus payments within the quarter that the project completed. In 2016, I completed two massive projects that both ended in Q4 2016 (calendar year).

In 2017, based on prior received bonuses, I had every expectation that I would be (shortly) receiving my bonus for the completed projects. Our annual reviews were done in January 2017 with the results announced March 10 2017. I received a job offer from another company that needed me to start prior to March 10 2017. Rather than lose the job opportunity and waste the first company's time and money diddling around doing nothing while waiting for the review, I gave notice; my final day at the company in question was Feb 17 2017.

I was informed that the bonus policy had recently changed, and since I was not employed on 3/10/17 I was not eligible for the bonus for the work completed in 2016. My former boss confirmed that I had a substantial bonus that was due to be awarded to me on 3/10.

Do I have a leg to stand on to pursue this bonus?