General question, How do you request clarification on a law? I have corresponded with the state of Tennessee in many occasions trying to get clarification of laws, however generally I receive answers from people within individual departments as to their interpretation of the law, or the way their internal departments handle things.
When you ask an agency for a "clarification" of a law, what you get is its interpretation of the law. The agency's interpretation of the law is what will apply unless and until someone challenges that interpretation in court. The court will have the final say on the meaning of the law. If you want an opinion of how a court would likely rule on how the law is applied, well, that is what lawyers are for.
I don't know what you mean by "legal interpretation" of a law. If you want a determination that is binding on the state, then you sue the state and get a court to rule on it. If all you want is to know what the law says and how a court would likely interpret any part of it that is not clear, again that is what lawyers are for.
There is no statute or regulation in TN that states you have a right to a license without a photograph other than for persons over age 60 who already had a license as of Jan 1, 2013 without a photograph and wish to renew that non photo license. The statutes set up a basic requirement that photos are required on all licenses unless there is an endorsement on the license that a photo is not required. Moreoever, federal law requires that all REAL-ID compliant licenses have photographs, and REAL-ID compliant licenses are the preferred licenses for the state to issue. The implication from these laws is that after Jan 1, 2013 no new license will be issued without a photograph and no renewal without a photograph unless you qualified for the age 60 exception and already had a valid non photo license. So absent some court decision that says that under the current statutes you have a right to get a non photo ID license it appears the Department would be within its power to deny issuing a non photo license. Consult a Tennessee attorney to see if there is some way to get a non photo ID license now.
Note that if you do succeed in getting a non photo license, it will not be REAL ID compliant. That means you cannot use it to enter any federal facility, to enter any area secured by the federal government, including passing TSA security at airports. As a result, you cannot use it get through security to board airplane, to enter a federal courthouse or federal building, etc. Also note that under Tennessee law you need photo identification to vote, and thus the non photo license would not be good ID for voting.