However if for example, someone could go and buy some regulated //marijuana legally from a store, they're more likely not going to go to black market. //
Yeah right. Just like those who smoke tobacco are far more likely to go to their local shop and pay £10 a packet instead of getting them from their neighbour who brings suitcases of them back from abroad and sells them for £5.
//Home brewing is allowed?//
Indeed it is. Home distillation of alcohol, however, is not.
//Danny, many county's have actually decriminalised cannabis. teesside for example. It is up to the chief of each county how they react and act.//
No they haven’t and no it’s not. Some police forces do not enforce the law (i.e. they have abrogated their responsibility). That doesn’t mean the offence has been decriminalised. It is not within a police chief's gift to "decriminalise" offences.