It's because most of the laws governing penalties for drug use are not created (and are often not enforced) by local jurisdictions. For example, Federal sentencing guidelines are made in Congress.
Local jurisdictions, when they do participate in enforcement, are incentivized on convictions and other metrics and alignment to the Federal system is better. So, even if the local police, DA, judge and others in the system are national minorities, but local majorities, they are still working for the national majority policies.
Local jurisdictions, when they do participate in enforcement, are incentivized on convictions and other metrics and alignment to the Federal system is better. So, even if the local police, DA, judge and others in the system are national minorities, but local majorities, they are still working for the national majority policies.