In reference to smack, I doubt many (if any) paras have sold heroin. Blow, E's, Coke, Speed, Valium- yes... but even they know that heroin would be a step too far, the paras need to have at least some degree of support to survive, perhaps unlike most criminals.
I think it was in the late 80's/ early 90's that some loyalists started selling E's & speed. Prior to this dope was pretty much the only thing around (and even then not half as plentiful as in Britain). I suspect that the paras may have turned a blind eye to ordinary people selling it. In the 90's some prominent UDA figures like Johnny Adair started making a fair bit of money from dealing pretty much all the drugs listed above (except H).
The Loyalists have always had a culture of profiteering; not all of them liked it but they accepted it. Drugs were relatively slow to arrive in Northern Ireland though. Johnny Adair in particular despised some of the loyalist drug dealers. His attitude was that he was off the hook as his unit were very busy assassinating, a 'work hard play hard' sort of attitude. The UDA had many drug dealers until recently, including 4 of their 7 'brigadiers', the leaders whom were sometimes celebrity cokeheads. The slightly smaller and more disciplined UVF had a largely anti dealing leadership, but had many members involved in it. The very small LVF was probably 95% drug dealing and 5% murder in the last 10 years.
Now the Loyalist paramillitary's are cleaning up their act, and in some areas people caught selling drugs (including paramillitaries) will recieve punishment beatings. Now you have the strange situation where in South Belfast no one has 'permission' to sell drugs, yet extortion is tolerated. In other areas drug dealing has continued, but extortion is outlawed. But you do get the feeling that Loyalist criminality is being wound down. At the moment a feud may spill out between anti drugs UDA men and pro in suburban Belfast.
On the republican side it's probably more confusing. There was a time (and no so long ago either) when an IRA member caught profiteering would be expelled from the organisation, maybe even punished. Drugs would have probably resulted in a kneecapping. Some people were killed for selling drugs, and a republican splinter group was crushed by the IRA in the early 90's soley because they dabbled in dealing. At some point this has obviously changed.
I get the feeling that when the Good friday agreement came about, the IRA stopped making an effort to curb drug dealing, especially in their own ranks. I would assume that many Republicans took the chance to get a slice of the drug dealing pie instantly, but it's hard to comprehend their confidence given how against drugs and profiteering the leadership were the second before peace. I doubt the IRA leadership are involved in drugs (though the sophisticated Northern Bank Robbery must have been approved/instigated), and I would assume that most of those involved are more or less renegades albeit ones who very much use their past IRA credentials to remain in control.
I suppose that one of the things about paramillitaries is that those with a criminal record have few job prospects, and so crime is a very easy option. I would hazard a guess this is one of the reasons why the IRA leadership reversed their anti profiteering policy. The IRA dont seem to be doing anything to stop drug dealing at the moment, but as they have more or less disbanded and probably have stopped meting out 'restorative justice', this isnt too surprising. The Loyalists in some areas have done a lot to curb dealing (effectively denying themselves of good revenue), but then they by and large still have their organisations in place and wont get in too much trouble with the govt if they are seen to be dealing with their own criminals.
In some cases in post ceasefire Northern Ireland, ex loyalists & republicans have been known to do a bit of dealing amongst themselves.
