Sweetpea do you know of the landmark case vs. County of San Diego? They didn't want medical marijuana but the state did, as did the residence. A sheriff, "doing his federal duty" as a civilian tried to help the DEA bust a dispensary run by a man in a wheelchair. The bust did come with the aid of the Sheriff's dept (illegal action there) and the court case went to the supreme court. Inhumane treatment of the prisoner in the wheelchair was a large part of the stories. Anyway, long story short, the government had to give back the marijuana and all assets seized like the plants, the cash register, the money from the safe, etc. Well some of it went missing, & in other cases the government flat out destroyed the marijuana. The government agencies involved had to pay the street value of the marijuana seized back to the man.
The government is NOT busting legal growers, its just not worth it, but they do investigate and visit on a moments notice. However, fools are pushing the laws and doing things literally illegal and those people are getting busted. For example, a large grower / dispensary here in Oregon got busted last year not for doing things according to state laws, but for selling illegally to people who do not have a prescription.
As for busting people who grow in State & National Parks... I would GLADLY help track down these grows if it lead to legalization in the US.