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Apologies, I was talking about whisky, the real thing, from Scotland.  My observation was not really to try to convince anyone to drink Scotch against their will but to correct the blasphemous notion that real Scotch was made from anything other than barley!
This is gluten-free and defined as such by the Coeliac UK and by other coeliac societies in Europe.
Yes, barley does have hordein (gluten) in it, but this is not in the distilled product called whisky as made in Scotland.  I don't know about elsewhere though my understanding is that this is how all 'real' whisky is made.  There is plenty of scientific stuff on it if people care to look.
This does not mean that even 'real' whisky does not agree with some people any more than any other drink or food. It's just not because of gluten.
Some subscibers will yawning loudly over this issue which has run many times on this Listserv.  
Below is some of the correspondence over the years - some of these discussions go back to the age of a decent single malt like Talisker.
Incidentally, lot of the flavour of Scotch whisky comes from the barrels (sherried or not) and the water. The barley is less important (unlike beer). On the lovely and rather under-visited island of Islay, a holy grail for whisky enthusiasts, the two famous distilleries of Lagavulin and Laphroaig are almost adjacent but the whiskeys taste quite different.  Personally I find the iodine in Laphroaig a bit overwhelming for an apperatif but fantastic for a hot toddy when you have a cold.  PS I am not being paid by either the Scottish Whisky Association or Island Tourist Board for this information but next time I have to write this, (and I fear there will be a next time) I might ask them for a very large fee.  I will however, confess to a Scottish husband and a son called Archie!
Charlotte, Oxford, UK
"America, land of the free, but not (yet) land of the gluten-free." Just kidding.
Listserv correspondence on whisky/whiskey since 1998 ish, in no particular order and with apologies if it the format goes weird:
"Spirits now are distilled in column. Stills containing 20 or more perforated plates in each column.  Steam rises through the columns stripping the alcohol from fermented mash.  Alcohol vaporizes at 78.5 degrees C but gluten or gluten fragments are not vaporized and do not go through the still.  In the case of gin, vodka and the major components of Canadian whisky blends, the base spirit is redistilled through a multicolumn still with three to five columns to remove fusel oil and other impurities.  This redistillation step further reduces the  ossibility of protein carryover into the final product.  It is concluded that distilled beverages, fortified wines, white distilled vinegar and alcohol based drug and extract products do not contain measurable amounts of gluten or gluten residues and therefore must be considered acceptable for a gluten-free diet."

" I went to a Johnny Walker Scotch Tasting last week, hosted by a gentleman who has worked for decades blending whisky for that company, which owns 40% of all the distilleries in Scotland.  And I asked this man whether the mash (or whatever it's called) is ever added back in after distillation.  The answer was, "No."  That stuff, he says, is fed to the cattle.  Most of the flavor comes from aging in Spanish and American Oak Casks that previously held sherry or whisky. Of course, this isn't scientific, and it doesn't PROVE that Scotch is GF.  But it leaves me (even more) comfortable that there is no reason for me to avoid drinking Scotch whisky. "

 "There is a Scotch Whisky Web page which has details of the double distillation process used to produce the pure alcohol which is then diluted with WATER and put into used sherry casks, which give the flavour.  I have it on the best authority that NO wort is ever returned to the distillate but you don't have to believe me - go there and find out yourselves. http://www.scotch-whisky.org.uk/frame.htm"

 "The discussion on skotch and other alcoholic drinks prompted me to make a search on the net and I came across Skotch Whiskey Association. I e-mailed them asking about the gluten status of whiskey. Apparently whiskey is ok."

"Thank you for your email. The distillery process means that no cereal residues survive through into the final spirit, thus celiacs should be able to enjoy Scotch Whisky without any health concerns."

 "Almost all responses to the question of whether or not Scotch whisky is gluten free were that it is GF with many responses coming from reputable sources such as chemists or distillers.  The only responses different to this were a small number where people were unsure.  So, while individual should decide for themselves, all evidence seems to point to all Scotch whisky being GF."

 "Thank you for your enquiry through our Macallan website. first advice is to contact doctor/pharmacist/dietician as we are not medical experts we can say however that our distilled products do not contain any gluten from the original cereal base and would confirm we do not add in any undistilled material

Yours sincerely Jason Craig The Macallan"

 "Gluten is a healthy sized protein. It will not distil over. However, whether distilled liquors consist solely of the clean distillate I don't know."

 "In regard to your question about gluten, I have good news. Although it

is true that corn, rye and barley malt (which contain gluten) are

primary ingredients in our Jack Daniel's Tennessee Whiskey, any gluten

that might be present is entirely removed in the distilling process. I

checked with our chief chemist, George Stone, and he confirmed that this

is correct, with the exception of Gentleman Jack, which has some color

and flavor added. We recommend that you obtain your physician's

clearance, but based on our knowledge, Jack Daniel's is gluten-free."

 "The Dietetic Association has agreed on new standards for a gluten free diet. It

does include vinegar, alcohol, (rum, gin, whiskey, vodka)"

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