Obviously there is a question about if we should be concerning ourselves with law and legislative purposes in pursuing liberation for animals. (The discussion on the last chapter of Calarco's book pursue some these questions over here). However, such a question could be rendered somewhat moot in a court case currently facing the Supreme Court, U.S. v. Stevens. Under considerations is a law banning the commercial sale of images and recordings of cruelty towards animals. You can get a good look at the case by reading this Chicago Tribune article and this NY Times article. The law was designed for stopping the selling of recordings of dog fights, and also crush videos. Crush videos are a sexual fetish videos in which women, either in high heels or bare feet, crush the bodies of living animals. There are certain free speech issues, and certain issues dealing with the present case itself and also potential for misuse of this law. None of those things do I really feel like going into.
However, also under consideration is if preventing animal cruelity constitutes a compelling state interest. When the Third Circuit court decided that the law was unconstitutional, it also determined that preventing animal cruelity was not a compelling state interest. The Supreme Court could rule without addressing this question at all, or it could rule in such a way that would set a precedent that could potentially gut the ability of the government to pass laws protecting animals unless it could also show that such laws also served some human interest.
If you are interested in pursuing the legal ramifications of all of this, I suggest you check out this post which contains links to oral arguments and an brief filed by animal law professors.