Several issues are at work here. A legal issue is at the heart of the question, but perhaps the real answer shouldn't be the best defense, but the best treatment.
The "friend" has been picked up more than once for making the poor, dangerous, and criminal decision to drive with diminished capacity. For one who is paid to operate aircraft, the judgement exercised in operating a motor vehicle while not fully in control shows a dangerous trend; it speaks to overall judgement.
Alcoholism is definitely a disease; or those who think a disease only involves a living pathogen involving a body, do a little research and eduate yourself. An addiction is a disease. Many mental issues are diseases of the mind, and often of the body, too. Alcoholism is both.
Regardless of what it is, we have a trend. This isn't a mistake made long ago; this is a repeat trend, an makes one ask how many times the "friend" has operated intoxicated and not been caught. There is no excuse, and there is never an excuse. That it holds wide public acceptance is a tragedy of epic proportions, but does not make it excusable.
One who undertakes to fire a rifle down mainstreet on a quiet winter night wouldn't have any public sympathy, but one who undertakes to become intoxicated and operate a motor vehicle weighing thousands of times that of the rifle bullet and posessing the potential to do significantly more damage is given a pass...unacceptable.
Tell your "friend" to seek an attorney and seek help; he needs both. AA isn't for losers; it's for those seeking to gain control again. He needs to wake up and admit he has a problem, and seek to fix it. Alcoholism is never "fixed;" it doesn't go away, nor is one ever "cured." Seeking to fix it is a lifetime effort that requires unending effort and vigiliance, but there's no alternative and no excuse for doing otherwise. Hopefully he or she gets the help needed.