I have not read the dark side post but I did look at your post itself and the answer to your question is yes, a state can impose a ban on anything it wants. It is called the home rule principle and its basic premise is that each state or body is sovereign. However, that does not mean that state legislation can be made willy nilly. There are certain criteria that need to be met (the law student above would be better at addressing this as it's been a long time since law school) in order for a statute to withstand judicial muster. Those depend on what the actual issue is and how it is framed. For instance, lawyers being the slimy bunch that they are, we could make a claim that a ban on a certain item is an unfair burden on a certain suspect group within the community and that the law as applied is unconstitutional due to its discrimin
atory practices. Basically, you are suggesting that a certain group has lost rights and privileges which are afforded to other groups. It's a big stretch of the imagination, but you get the idea of how the law works.
Bottom line is that most sovereign bodies can make up their own rules as they go along, and that's that. A good analogy would be a city like Chicago which imposes a handgun ban. If you bring a handgun into the city, even if it's not on your person and sits in a drawer unloaded in your house, you are subject to prosecution. The overall law in Illinois states that you are allowed to possess a firearm after you have obtained the proper license. This applies to the entire state of Illinois, however, Chicago contradicts this rule and does not allow the possession of firearms.
Extrapolating that logic to your case at hand, the United States as a whole can allow people to have reef tanks, and California could turn around and legislate against it, but that's they're perogative.
There is no real answer to your question (at least what I think your question was) without having a better grasp of California law. I only know Illinois law, and a ban here would work.