He can't. The judges of these courts are not the fatwa issuing mullahs you imagine them to be. These people are well-versed in law, at least to the extent of cases they deal with and their limits of jurisdiction. The fatwa factory in India is a separate institution called Dar-ul Uloom Deoband.
If a judge proclaims that the wife be killed like you said, the same thing happens as what would happen if a normal civil magistrate orders the same thing. The order will be appealed in a higher court and the judge will be hounded in media.
The shariah court only stands as a symptom of the separate civil code which we have. There is nothing to get alarmed by the court as such. They were in place for a long time now. I would be happy if the jurisdiction of the civil code excludes alimony and child support, equal marriage and property rights for women.
Beyond that there is not much gain in pushing for a uniform civil code. Any Indian members here disagree? @
Bang Galore ?