Drug Policy

Legalizing marijuana in places where it's illegal, without interfering with state policies that have already legalized it would be an improvement. There is no evidence that legalization has led to big negative effects and further legalization would reduce criminal involvement

This completely depends on which supporting rules are put in place fo oversight, distribution, access control, enforcement, taxation. Done well, this would improve on the current regime. But even our current deregulation regime is glutted with crime and foreign crime involvement

I am not sure what you mean by social welfare but it would be great if everyone in prison for illegally selling marijuana in the past get pardoned and such imprisonment stops for ever

Social welfare can mean a lot of things, and such a policy would effect many groups very differently.

My understanding is that the compliance costs required for research labs to study the efficacy and harms of Sched 1 drugs are much higher than for Sched 3. Lowering the barriers to such studies, given the widespread use of cannabis under state laws, seems a worthy policy goal.
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I would go further and legalize it, as in Massachusetts

Most states already allow medical marijuana use. So, in most states, it will have no effect. It may be best to decriminalize completely.

Marijuana is no worse than alcohol. Like alcohol, its use should be regulated to keep it away from minors and to prevent harm to others. Law enforcement efforts would be better spent on dealing with abuse of alcohol (and marijuana).

My sense of the evidence in states that have legalized is that there are very mixed results.

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It is a step in the right direction, but not sure about size of impact.

It would still be illegal under federal law with potentially substantial penalties. Perhaps enforcement would be relaxed, but perhaps not.

The relative dangers of these drugs are now well known. Marijuana is legal in many states.

Direct effects: lower cost for sellers through a tax change, and an upward shift in demand. Hence sales will increase, leading to more and better targets for armed robberies, since it will still be a cash-only business. There will be winners and losers. On net, ambiguous.

Schedule I for marijuana is a decades-old mistake that created massive enforcement costs (direct and spillover). Moving away from it helps. Further moves in that direction may be optimal.

Not difficult.

Marginal move to catch up with reality, voters and state laws. Symbolically: bigger inflection point on War on Drugs. But whatever one thinks of that "war", having heroin and marijuana in same class is no longer justifiable. Uruguay and Canada doing fine with legal marijuana.