Legal Question in Business Law in California

Corporations Code section 400(b) seems to prohibit this, but a legal exception to payment of an equal dividend to the current holder of each share seems to exist under Corporations Code section 701 regarding "record date".

As you probably know, corporations in declaring dividends usually declare them as "$X per share payable on Y (date) to holders of record as of Z (date)." Thus, a situation similar to what you describe could occur legally -- a more-recent holder getting less than a longer-term share holder -- because of two separate, consecutive dividends with different record dates, one of which was before the new shareholder got his shares.

Further note that CC 400(b) would allow different dividend treatment of shares that were issued in different "series" which essentially calls for a separate class of stock, but there is no indication in your question that the new shareholder received shares in a different series.