You're just being silly at this point.
We already precisely covered why your suggested sustainable fin ban option was not practical. That WOULD have made the ban ineffective by giving cover for restaurants to bring in shark fins caught illegally while claiming they were all from legit sources, the illegal sources would certainly be far cheaper. (By contrast the current law means if genuine shark fin soup is offered in the future, they are violating the law.)
The US DOES have a law which is supposed to prevent true "blood diamonds from being imported, the problem is it actually doesn't always work.
http://en.wikipedia.org/wiki/Blood_diamond#Conflict_diamond_campaign
Note that this is with a rather expensive item where the cost of tracking and regulation per individual sale is more viable.
Fair trade coffee is obviously an applies to oranges comparison. The obvious question is "how on earth are you going to define what is legally considered fair trade?" If you specify that one of specific organizations already doing the certifying gets to definite it, you're giving an incredible amount of power to an organization utterly unaccountable to California voters. Alternately if you try to specify all the details of what qualifies as fair trade in the law itself, you're creating an incredibly ugly regulatory situation which would basically fit in with conservatives' worst nightmares regarding how they see what liberals want creating problematic regulations which causes government to micromanage how businesses are run.
A final point regarding the cultural argument you keep on bringing up is that it doesn't fit with how California has also already passed a law which will ban foie gras in 2012.
http://en.wikipedia.org/wiki/California_foie_gras_law
While you can argue that not everyone in California eats foie gras either, it certainly isn't a dish that is culturally Asian in origin. (Just look at the name.)
For that matter, even though clearly the overwhelming portion of California voters definitely eat eggs in some form, California voters were perfectly willing to pass a law banning conditions commonly seen in "battery farms" of the time in which a considerable portion of the chicken eggs laid in California were produced.
http://en.wikipedia.org/wiki/California_Proposition_2_(2008)
The point is that Californians are clearly perfectly willing to pass laws in reaction to animal cruelty or environmental issues regardless of whose culture it impacts and the claim this is all about discrimination against Chinese simply doesn't make sense.