Marijuana dealer should be arrested only if the drug is illegal in their area. If it is, then they are breaking the law and should have to pay the consequences. If the drug is allowed and legal in their area, then they should be left alone because they aren't doing anything wrong.
The conditions for not being arrested are that they do not have the intent to sell to minors, sell weed laced with another drug, or infringe upon any plausible drug laws. Just like alcohol and tobacco, they are legal and readily available everywhere you go. Weed will end up being the same way, and so I don't believe that dealers of it currently should have to undergo jail-time for what will eventually be commonplace.
I believe marijuana dealers should be fined heavily when caught. The substance is illegal therefore it should not be allowed to be traded in any quantity. The fine should be of such a sum that would make potential dealers hesitant in thinking about dealing since the consequences far outweigh any potential income. A simple slap on the wrist or changing the fine to a lower fine such as misconduct does not solve the problem.
We would reduce spending on a criminal enterprise that will forever exist, and drastically increase our Nations wealth, if marijuana dealers were treated like business owners instead of arrested. They should contribute to society by paying taxes on their sales. With the paid taxes a regulatory committee could be formed to monitor these businesses and their products to ensure standards are met and licenses are valid. If people realized that marijuana is illegal due to threatened cotton yields thanks to hemp, and understood the true history of marijuana, many citizens that feel threatened by this idea would be more open to creating legal entrepreneurs out of marijuana dealers.