Cheezuz, live and let live, ffs!
Unless their activities are affecting your life, or causing grief, just **** ignore it!
The fact that you can smell it probably means it's just an 'amateur' operation. Proper Skunk farms are hermetically sealed, to avoid dog detection.
Maybe pop round to have a quiet word about the smell. That's all you have to do. There's people noncing kids, and doing all sorts of nastiness, that's far worse than growing a bit of weed. Let the police concentrate on catching the real scum.
The amount of propaganda against weed is totally disproportionate, when you consider that it's Crack and Smack that's doing the real damage. And have you any idea how much Coke gets shifted, by seemingly respectable city bods? Most lucrative drugs market there is!
And it's all those Coked-up traders, that have fecked the economy, you know...