If one of the alternative acts required by an obligation is such as the law will not enforce, or becomes unlawful, or impossible of performance, the obligation is to be interpreted as though the other stood alone.
Cal. Civ. Code § 1451
Alternative Obligations
Enacted 1872.
Official source: California Legislative Information. Reproduced from public-domain California statutes; confirm against the official source for the current text. Not legal advice.