It's likely that the abortion in this case would have been illegal in California. It's hard to say for sure, because California prohibits abortion after medical viability rather than setting a strict week limit, but it happened at week 23 when many fetuses are viable.

Mostly, for my own edification, but did similar ambiguities arise during the implementation of the Fugitive Slave Act? If so, how where they handled?

I don't want to say "similar", because chattel slavery was uniquely bad, but even in areas that wouldn't enforce the Fugitive Slave Act forced prison labor was pretty common at the time. There was also the question of what should happen to people who conspire to violate the Fugitive Slave Act, although my understanding is that in practice it was impossible to get northern juries to convict them.