The federal government should not be harassing sick people and their caregivers. Attorney General Eric Holder Jr. has made the right decision, calling off prosecutions of patients who use marijuana for medical purposes or those who distribute it to them  provided they comply with state laws.

It is a welcome reversal of the Bush administration’s ideologically driven campaign to prosecute dispensaries, even in states that had made medical uses legal and often with overwhelming popular support.

The Justice Department sent a memo this week to prosecutors in the 14 states that allow the use of marijuana for medical purposes, suggesting that they instead pursue significant traffickers of illegal drugs, including marijuana. Mr. Holder made it clear, quite properly, that his department “will not tolerate drug traffickers who hide behind claims of compliance with state law to mask activities that are clearly illegal.”

The memorandum also stressed the importance of cracking down on the criminal distribution and sale of marijuana, which remains the largest source of revenue for the Mexican drug cartels and a frightening driver of violence and lawlessness on both sides of the border.