Rules of the respective institution not the full law of the land. Even if you brought a 14th Amendment case against a state for not having English as their official language, it would not stand up as there is no element of the constitution to incorporate.
So, what we have is a UN-OFFICIAL, OFFICIAL ENGLISH Language for most of the country. I say most, because of my limited knowledge about the State of New Mexico, if I'm not mistaken New Mexico either recognizes Spanish in their State Constitution, or some how puts it {Spanish Language} on par with English.
Anyone from New Mexico, your help is needed.