What happens to cannabis sellers when possession is “decriminalized”?

As a practical matter, what happens to cannabis sellers when possession is “decriminalized” – when a consumer: 

1. Faces zero consequences? (There’s zero incentive for possessors to turn on sellers and turn them in.) 

2. Faces minor consequences? 

Does law enforcement lose heart and tolerate illegal sales?

Claude A.I., WHICH IS NOT TO BE TRUSTED, replies:

These are sharp practical questions, and the real-world evidence from various decriminalization regimes gives some fairly clear answers.

When consumers face zero consequences

You’ve identified the core enforcement mechanism correctly: informants. Most low-level drug prosecutions historically depended on threatening buyers with possession charges to flip them against sellers. Remove that threat entirely and you lose that tool almost completely. In practice, what happens:

• Street-level and mid-level sellers become nearly prosecution-proof without other investigative methods (surveillance, undercover buys, financial investigations).
• Law enforcement shifts toward those other methods, but they’re far more resource-intensive. A “buy-bust” using an undercover officer is expensive compared to arresting a buyer and flipping them.
• Illegal markets don’t disappear — they often stabilize or even expand in the short term, because the downside risk for buyers evaporates and demand rises.
• Portugal’s full decriminalization (2001) is the most-cited case. Illegal sellers still exist and still get prosecuted — but enforcement shifted almost entirely to supply-side methods rather than buyer-cooperation.

When consumers face minor consequences (fines, civil penalties)

This is actually the trickiest scenario, and arguably worse for enforcement than zero consequences:

• The threat is too small to meaningfully flip buyers, but still creates enough friction that some buyers migrate to legal markets (if available) or become resentful of enforcement.
• Sellers can credibly tell buyers “you won’t snitch over a $100 fine” — and they’re largely right.
• Police discretion explodes. Officers know a possession citation leads nowhere prosecutorially, so many simply stop making the effort. This is well-documented in states that decriminalized before full legalization (California pre-2016, New York before 2021) — possession enforcement essentially collapsed in practice years before the law changed formally.

Does law enforcement lose heart?

Yes, to a significant and well-documented degree — but with important nuances:

• Street-level officers lose motivation fastest. If a patrol officer knows a possession arrest produces nothing — no prosecution, no informant, no case — they stop making arrests. This happened visibly in NYC even before formal decriminalization; NYPD marijuana arrests dropped dramatically once the DA announced non-prosecution policies.
• Specialized narcotics units adapt better, because they were already using surveillance and financial tools rather than buyer-flipping. The DEA’s approach to cannabis trafficking changed less than local patrol behavior.
• Political signaling matters enormously. When a DA announces non-prosecution of possession, it implicitly signals to sellers that the whole ecosystem is deprioritized — even if that wasn’t the intent.
• The illegal seller market, paradoxically, can face more enforcement pressure in some decriminalization regimes, as police redirect from easy possession arrests toward supply-side investigations to show they’re still doing something. This happened in some Colorado and Washington counties after legalization.

The bottom line

Decriminalization without legal supply (licensed sellers) is widely regarded by criminologists as the worst of both worlds for market disruption: you remove the enforcement tools that target buyers while leaving illegal sellers as the only supply. The illegal market loses its risk-based price premium partially, but doesn’t face meaningfully greater enforcement — so it persists, often undercutting legal markets on price while losing some customers to convenience and quality of legal sources. The buyer-as-informant pipeline was a genuinely significant enforcement mechanism, and its loss is real, not just theoretical.