One, Governor Goodhair can't stop the execution. The Texas Board of Parole and Pardons makes the decision on executions, pardons and paroles. The Board affirmed the execution order. Goodhair can't stop it.
Second, Jose Medellin did not take the Mexican national position until 1997. Four years after his trial. Medellin said he told both Houston police and Harris County sheriffs that he was a Mexican national upon his arrest, but this story falls apart on it's own when you consider that neither Medellin nor his attorney brought up this point during his trial, his sentencing phase, nor in his appeals until the Mexican government brought it up to him in 1997. The only question that remains is what Medellin will have for his last dinner.