я бы назвал это так

здесь, очевидно, имеется в виду не специализация среди торговцев алкоголем, а вообще в какой конкретно отрасли бизнеса из общего списка направлений деятельности специализируется данная организация

I think several terms could work. I like 'class' as in 'liquor license class'.

From http://www.revenue.wi.gov/faqs/ise/atlicns.html:
What types of alcohol beverage licenses are there?
Class "A" fermented malt beverage licenses allow retail sale of fermented malt beverages (beer) for consumption off the premises. Examples: grocery or convenience stores.
"Class A" liquor licenses allow retail sale of intoxicating liquor (including wine) for consumption off the premises. Examples: liquor stores or grocery stores with full liquor sales sections.
Class "B" fermented malt beverage licenses allow retail sale of fermented malt beverages (beer) for consumption on or off the premises. Examples: restaurants, "beer bars."
"Class B" liquor licenses allow retail sale of intoxicating liquor (including wine) for consumption on the premises, and wine in original containers for consumption off the premises. If the community elects to, it may also permit sale of not more than four liters of intoxicating liquor (there are no limits on wine), in the original container, for consumption off the premises. Check local ordinances for the allowance. State law also allows carryout of a single, opened (resealed) bottle of wine if sold with a meal. Examples: taverns and restaurants with full alcohol service.
"Class C" wine licenses allow the sale of wine for consumption only on the premises and allow the carryout of a single opened (resealed) bottle if sold with a meal.
Temporary Class B licenses (often called picnic licenses) allow retail beer and/or wine sales, at temporary events like fairs and festivals. Only certain organizations qualify for such a license. They must be bona-fide clubs, county or local fair associations, churches, lodges, or societies that have been in existence for at least six months.
There are several other locally issued licenses or state issued permits that allow retail sale of alcohol beverages under certain circumstances. The licenses listed above are the most common, however.

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Note added at 43 mins (2012-02-17 19:43:29 GMT)
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@Tom Fennell: The text from revenue.wi.gov was not in any way meant to imply that the "specialization" that Nadezhda is asking about is equivalent to the classes established by the state of Wisconsin. That would be absurd. I was merely providing examples of how the word 'class' might be used to express the various types of "specialization" of a (Russian) liquor license. I think Amy's suggestions are great--and so is mine. :)

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Note added at 45 mins (2012-02-17 19:46:04 GMT)
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In other words, if the state of Wisconsin had chose to "specialize" their liquor licenses using the terms "Category A", "Category B", etc., it would have no bearing whatsoever on the validity of using the term 'class' or 'category' for a translation of "специализация".