The prohibition of marijuana has been a costly failure, one that has undermined police efficacy, wasted resources and made our communities less safe by empowering criminal gangs. But in the wake of Colorado and Washington voters’ recent passage of marijuana legalization initiatives, Congress has a unique opportunity to allow changes in this failed policy without officially endorsing legalization.

As police veterans from these two states, we write from the perspective of former believers who have lost their faith in prohibition. We have seen how, as a result of these laws, police officers — once seen as protectors and guardians — are now looked upon as invaders and aggressors by many in the communities we are sworn to protect.

We have seen that once we lose the support of that community, our jobs become impossible. More crimes go unreported. Witnesses are unwilling to talk; investigations go nowhere. We are looked on as the enemy.

We’ve spent billions of dollars and arrested millions of people trying to curb marijuana use in this country over the past 40 years. We’ve used our police and our courts’ time prosecuting petty dealers and users while serious crimes — murders, burglaries, rapes — went unsolved.

Meanwhile, by making marijuana trafficking extremely profitable by making it illegal, we encouraged street gangs and drug cartels to participate in that trade. Now these groups are stronger and more violent. According to the Justice Department, Mexican drug cartels have set up operations in more than 1,000 U.S. cities. In Mexico, an estimated 60,000 deaths have been attributed to these cartels since 2006.