WASHINGTON – Two decisions Monday, one by a federal judge in New York and the other by Attorney General Eric Holder, were powerful signals that the pendulum has swung away from the tough-on-crime policies of a generation ago. Those policies have been denounced as discriminatory and responsible for explosive growth in the prison population.

Critics have long contended that draconian mandatory minimum -sentence laws for low-level drug offenses, as well as stop-and-frisk police policies that target higher-crime and minority neighborhoods, disproportionately affect members of minority groups. On Monday, Holder announced that federal prosecutors would no longer invoke the sentencing laws, and a judge found that stop-and-frisk practices in New York were unconstitutional racial profiling.

While the timing was a coincidence, Barbara Arnwine, president of the Lawyers Committee for Civil Rights Under Law, said that the effect was "historic, groundbreaking, and potentially game-changing."

"I thought that the most important significance of both events was the sense of enough is enough," said Arnwine, who attended the speech in San Francisco where Holder unveiled the new Justice Department policy. "It's a feeling that this is the moment to make needed change. This just can't continue, this level of extreme heightened injustice in our policing, our law enforcement and our criminal justice system."

A generation ago, amid a crack cocaine epidemic, state and federal lawmakers enacted a wave of tough-on-crime measures that resulted in an 800 percent increase in the number of prisoners in the United States, even as the population grew by only a third. The spike in prisoners centered on a rise in the number of black and Hispanic men convicted of drug crimes — blacks are about six times likelier than whites to be incarcerated.

But the crack wave has long since passed and violent crime rates have plummeted to 40-year lows, in the process reducing crime as a salient political issue. Traditionally conservative states, driven by a need to save money on building and maintaining prisons, have taken the lead in scaling back policies of mass incarceration.

Against that backdrop, the move away from mandatory sentences and Judge Shira Scheindlin's ruling on stop-and-frisk practices signaled that a course correction on two big criminal justice issues that disproportionately affect minorities has finally been made, according to advocates who have pushed for those changes.

'A sea change'

"I think that there is a sea change now of thinking around the impact of over-incarceration and selective enforcement in our criminal justice system on racial minorities," said Vanita Gupta of the American Civil Liberties Union. "These are hugely significant and symbolic events, because we would not have either of these even five years ago."

Michelle Alexander, an Ohio State University law professor who wrote "The New Jim Crow: Mass Incarceration in the Age of Colorblindness," an influential 2010 book about the racial impact of policies like stop-and-frisk and mandatory minimum drug sentences, said the two developments gave her a sense of "cautious optimism."

"For those of us who have become increasingly alarmed over the years at the millions of lives that have been wasted due to the drug war and the types of police tactics that have been deployed in the get-tough-on-crime movement, today's announcements give us fresh hope that there is, in fact, a growing public consensus that the path that we, the nation, have been on for the past 40 years has been deeply misguided and has caused far more harm and suffering than it has prevented," she said.

But not everyone was celebrating. William Otis, a former federal prosecutor and an adjunct professor at Georgetown Law School, described Holder's move as a victory for drug dealers that would incentivize greater sales of addictive contraband, and he suggested that the stop-and-frisk ruling could be overturned on appeal.

Otis also warned that society was becoming "complacent" and forgetting that the drug and sentencing policies enacted over the past 30 years had contributed to the falling crime rates.

Yet Chuck Wexler, executive director of the Police Executive Research Forum, a Washington-based research group, said many police chiefs agreed that it was time to rethink mandatory sentencing for low-level drug offenses. And he said departments across the country would examine the stop-and-frisk ruling in New York "to see if their practices pass muster."