Rand Paul is a US senator from Kentucky. He serves on the Foreign Relations Committee and the Homeland Security and Governmental Affairs Committee. The views expressed in this commentary are his own.

(CNN) The attorney general on Friday made an unfortunate announcement that will impact the lives of millions of Americans: he issued new instructions for prosecutors to charge suspects with the most serious provable offenses, "those that carry the most substantial guidelines sentence, including mandatory minimum sentences."

Mandatory minimum sentences have unfairly and disproportionately incarcerated a generation of minorities. Eric Holder, the attorney general under President Obama, issued guidelines to U.S. Attorneys that they should refrain from seeking long sentences for nonviolent drug offenders.

I agreed with him then and still do. In fact, I'm the author of a bipartisan bill with Senator Leahy to change the law on this matter. Until we pass that bill, though, the discretion on enforcement -- and the lives of many young drug offenders -- lies with the current attorney general

The attorney general's new guidelines, a reversal of a policy that was working, will accentuate the injustice in our criminal justice system. We should be treating our nation's drug epidemic for what it is -- a public health crisis, not an excuse to send people to prison and turn a mistake into a tragedy.

And make no mistake, the lives of many drug offenders are ruined the day they receive that long sentence the attorney general wants them to have.

If I told you that one out of three African-American males is forbidden by law from voting, you might think I was talking about Jim Crow 50 years ago.

Yet today, a third of African-American males are still prevented from voting, primarily because of the War on Drugs.

The War on Drugs has disproportionately affected young black males.

The ACLU reports that blacks are four to five times likelier to be convicted for drug possession, although surveys indicate that blacks and whites use drugs at similar rates. The majority of illegal drug users and dealers nationwide are white, but three-fourths of all people in prison for drug offenses are African American or Latino

Why are the arrest rates so lopsided? Because it is easier to go into urban areas and make arrests than suburban areas. Arrest statistics matter when cities apply for federal grants. It doesn't take much imagination to understand that it's easier to round up, arrest, and convict poor kids than it is to convict rich kids.

The San Jose Mercury News reviewed nearly 700,000 criminal cases that were matched by crime and criminal history of the defendant. Their analysis showed that whites of similar situation were far more successful in the plea bargaining process and "virtually every stage of pretrial negotiation" than their African-American and Latino counterparts.

I know a guy about my age in Kentucky who was arrested and convicted for growing marijuana plants in his apartment closet in college.

Thirty years later, he still can't vote, can't own a gun, and, when he looks for work, he must check the box -- the box that basically says, "I'm a convicted felon, and I guess I'll always be one."

He hasn't been arrested or convicted for 30 years -- but still can't vote or have his Second Amendment rights. Getting a job is nearly impossible for him.

Mandatory sentencing automatically imposes a minimum number of years in prison for specific crimes -- usually related to drugs.

By design, mandatory sentencing laws take discretion away from judges so as to impose harsh sentences, regardless of circumstances. Our prison population, meanwhile, has increased by over 700% since the 1980s, and 90% of them are nonviolent offenders. The costs of our prison system now approach nearly $100 billion a year. It costs too much, in both the impact on people's lives and on our tax dollars.

I want to go the opposite way from the attorney general. That's why I've partnered with Senator Leahy and once again will be reintroducing the Justice Safety Valve Act.

This isn't about legalizing drugs. It is about making the punishment more fitting and not ruining more lives.

The legislation is short and simple. It amends current law to grant judges authority to impose a sentence below a statutory mandatory minimum.

In other words, we are not repealing mandatory minimums on the books -- we are merely allowing a judge to issue a sentence below a mandatory minimum if certain requirements are met.

We need this legislation because while there is an existing safety valve in current law, it is very limited. It has a strict five-part test, and only about 23% of all drug offenders qualified for the safety valve.

The injustice of mandatory minimum sentences is impossible to ignore when you hear the stories of the victims.

John Horner was a 46-year-old father of three when he sold some of his prescription painkillers to a friend.

His friend turned out to be a police informant, and he was charged with dealing drugs. Horner pleaded guilty and was later sentenced to the mandatory minimum of 25 years in jail.

As I testified before the Senate Judiciary Committee, Edward Clay was an 18-year-old and a first-time offender when he was caught with less than 2 ounces of cocaine. He received 10 years in jail from a mandatory minimum sentence.

Weldon Angelos was a 24-year-old who was sentenced to 55 years in prison for selling marijuana three times.

Former federal judge Timothy Lewis recalls a case where he had to send a 19-year-old to prison for 10 years for conspiracy. What was the "conspiracy"?

This young man had been in a car where drugs were found. I don't know about you, but I'm pretty sure one of us might have been in a car in our youth where someone might have had drugs. Before the arrest, according to news reports, this young man was going to be the first in his family to go to college.

Each case should be judged on its own merits. Mandatory minimums prevent this from happening.

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Mandatory minimum sentencing has done little to address the very real problem of drug abuse while also doing great damage by destroying so many lives, and most Americans now realize it.

Proposition 47 recently passed in California, and it has spurred a cultural change in the way nonviolent drug offenders are treated, resulting in more than 13,000 fewer prisoners and a savings of $150 million, according to a Stanford Law School study.

Pew Research found that 67% of Americans want drug offenders to get treatment, not prison, and over 60% want an end to mandatory minimum sentences.

I urge the attorney general to reconsider his recent action. But even more importantly, I urge my colleagues to consider bipartisan legislation to fix this problem in the law where it should be handled. Congress can end this injustice, and I look forward to leading this fight for justice.