Chopping off a hand is aggravated assault and battery.
Honor killing is premeditated murder.
There should be no religious 'shield' or exemption for either, or for other practices which are by our (US) definition crimes.
Given that, a blanket law banning Sharia 'law' would be unconstitutional (free exercise of religion) so I agree with the court. Nonetheless, our secular laws should always remain supreme.