If Congress changes marijuana laws without allowing currently imprisoned pot offenders to seek new sentences, should this president or the next simply throw open the gates?

Clemency feels particularly appropriate for marijuana prisoners, who sit in cells for trafficking and dealing while state legislators argue over how to spend the revenues generated from pot taxes and newspapers tell us how to incorporate the plant in our cooking.

It should be cruel and unusual, indeed, to mete out life-without-parole-sentences for a drug so mainstream that Colorado is using state-collected pot taxes to build new schools…

But clemency, by its very nature, benefits only a small number of people. Even if President Obama were to grant 2,000 commutations over the next 21 months — an unprecedented number — there are roughly 100,000 drug offenders in federal prison. The vast majority would be left to serve excessively long sentences.