So? The first one who is arrested, charged, convicted, and jailed for blackmail (maximum sentence 14 years) will, by that, stop the others. And it is blackmail to make an unwarranted demand, that a person stop supplying alcohol, with menaces, threatening them with whipping etc. with a view to gain for oneself or intent to cause loss to another. Loss includes loss of property or money, whether permanently or temporary. It can be argued that trying to stop a shopkeeper from selling alcohol (or trying to remove alcohol they have), is with intent to cause them loss either monetary or in property.
The only defence , the facts being established, is to show that the defendant had reasonable grounds for making the demand and that the use of menaces was a proper means of enforcing it.
Conspiracy to commit blackmail is also an option; that the defendant with another or others agreed on that course of action, whether or not they carried it out.