A new execution protocol is under review, but Newsom's order will withdraw it.
"That is powerfully demonstrated by their approval of Proposition 66 in 2016 to ensure the death penalty is implemented, and their rejection of measures to end the death penalty in 2016 and 2006". "The intentional killing of another person is wrong".
"I do not believe that a civilized society can claim to be a leader in the world as long as its government continues to sanction the premeditated and discriminatory execution of its people", Newsom said in prepared remarks on Wednesday.
It does not provide for the release of any death row inmates from prison.
Mike Semanchik, managing attorney for the California Innocence Project - which works to exonerate inmates on death row - cheered the move.
While campaigning for a measure to repeal the death penalty in 2016, he told The Modesto Bee editorial board he would "be accountable to the will of the voters", if he were elected governor.
How did we get here?
Newsom's office said he can act unilaterally because he's enacting a moratorium, not changing anyone's sentence. What might have seemed avant-garde decades ago, isn't anymore: The governors of Colorado, Oregon and Washington state have issued moratoriums on executions in recent years.
Seventy-nine condemned California inmates have died of natural causes since California reinstated capital punishment in 1978.
United States trade deficit hits ten-year high
The latest report revealed that the trade deficit with China in December was $38.7 billion, by far the highest of any nation. There would either be "a good deal or it's not going to be a deal, but I think they're moving along very nicely".
California has executed 13 people since the U.S. Supreme Court reinstated the death penalty in 1976. The order will reprieve all individuals sentenced to death in California.
But Newsom's action will anger death penalty proponents.
The Association of Deputy District Attorneys blasted Newsom for "usurping" the will of the voters and "substituting his personal preferences".
"He's following in the footsteps of other governors who abused this power because they were frustrated by a law that they just personally disagreed with", Scheidegger said.
The executive order grants a reprieve to 737 inmates on the country's largest death row and halts the use of the death penalty in the state, according to the governor's office. "The number of men and women on death row who suffer from severe mental illness or impairment is shocking".
Another key point of Newsom's argument is the wrongful conviction and subsequent overturning of inmates on death row.
Newsom's aides said it has not yet been decided what will become of the execution chamber, or whether corrections officials have been told to top preparing for executions, for instance by running drills.
"The disparities are very real and raw to me now especially as I spend every week working on the issues of paroles and commutations", he said.