Lots of us try to buy local but I have been thinking about this while I am in France and comparing it to what I know of Australia, or really just South Australia. Keep in mind that South Australia is 1.5 times larger than France in area but France has 40 times as many people!
For me, in SA, local means a few things. First, it means from a friend or producer very close to my house. Next it means within about 100km, like the oats Andrew wrote about. Thirdly, it means in the state of South Australia, and finally it means in Australia. I have even added the idea of local including Asia, at times.
Most of the food I eat at home comes from my garden or very near my home - such as fruit from my mother and vegetables from growers like Tony Scarfo at Virginia. Most of the dairy and grains I buy come from the 100km zone, and from Paris Creek Dairy and Four Leaf Milling in particular. Most of the seafood and wine I buy comes from somewhere in South Australia and most of the rest of the things I buy, like bananas and toilet paper and seeds and other bits and pieces are grown or made in Australia. I included Asia when I was thinking of rice, coconuts and soy sauce etc. In Europe, these things come from the African continent.
France is divided into 96 departments, all numbered in alphabetical order (which makes looking for them on a map very difficult!!). (This is like dividing South Australia into nearly 150 little areas). Every food item you buy has the number of its origin prominently displayed. This area, Dordogne, is number 24, and nearly everything I have seen at the markets has this number or 47, Lot et Garonne, the next department to the west and actually where the market is situated. Although things like oranges, this time of the year, are clearly marked 'from Spain', which is the next country but only 2 hours away! Even the milk bottles have this information in number form and I just noticed that our current bottle of milk comes from just 2 departments away to the south.
I love France's system of identifying small areas by number or name, and in France everyone seems to want as local as possible because it is the custom to believe that the best of everything comes from your local area and the farmers over the hill or on the other side of the next town just don't produce goods of the same quality as the farmers nearest you! And produce from several departments away ... well.... it might just as well be from Mars! Of course this wouldn't work in the same way for South Australia because so much of it is arid.
We are very lucky in South Australia to be able to grow most things, from vegetables and fruit to milk and grains, grapes and seafood. I cannot understand why the SA government does not encourage the state to be as self-sufficient in food as possible. Instead they cut the growers' water allocations but do not cut water allocations to any other businesses in the whole state!