The New York City Bar Association has slammed President Donald Trump's commutation of Roger Stone's 40-month prison sentence for witness tampering and lying to investigators during a probe of the Trump campaign's ties to Russia, saying the move breached Trump's oath of office and violated the sanctity of jury proceedings.

In a letter to Trump, City Bar leaders said Wednesday the act of clemency, doled out to a longtime ally just before Stone was set to report to prison, amounted to a claim that the president was " beyond the reach of the law" he swore to uphold.

"That this irregular process was followed to afford dispensation to a close personal associate of yours is itself a cause of concern," the letter said. "However, when, as appears to be the case here, a president uses the pardon power to reward an associate for declining to provide a duly authorized federal prosecutor with relevant information about the president's own actions, the effects on our nation's Constitutional system—and our society's commitment to live according to law—are profound."

Congressional Democrats and other groups, including the New York State Bar Association, have widely denounced the commutation of Stone's sentence, which stemmed from Special Counsel Robert Mueller III's investigation, as an overreach of executive power that threatened the legitimacy of the American justice system.

In its own letter Monday, the NYSBA called the decision a "perversion of justice" meant to "save a political crony who was convicted by a jury of his peers of lying to protect the president."

The White House, in announcing the grant of clemency July 10, attacked the Mueller probe, prompting Mueller to issue a rare public statement on Saturday, defending his team in a Washington Post op-ed.

The City Bar said Wednesday also cited "serious concerns" about the president's public attacks on the forewoman of the jury that convicted Stone over political views that she had expressed in the past, despite the fact that the judge overseeing case had specifically rejected defense claims of juror misconduct.

In the letter, the City Bar said that Trump's comments undermined the apolitical role of jurors, who serve "often at considerable inconvenience and expense" to themselves.

"Jurors should be able to assume and perform their duty in a conscientious manner free of outside influence and personal criticism from their nation's president," the letter said. "We call upon you to cease such efforts to intimidate or excoriate your fellow citizens in ways that are merely self-beneficial and suggest that you—and your close allies—are above the law."

A federal jury in Washington, D.C., last year found Stone guilty on all seven charges brought against him, including lying to the House Intelligence Committee as part of its Russia probe.

Trump's commutation of Stone's sentence has sparked outrage particularly among Democrats in Congress, with Speaker Nancy Pelosi, D-California, calling for legislation "to ensure that no president can pardon or commute the sentence of an individual who is engaged in a cover-up campaign to shield that president from criminal prosecution." However, scholars are skeptical that any meaningful limits can be lawfully placed on the broad pardon powers established in the Constitution.

The City Bar said on Wednesday that it had not considered the question of whether there were grounds to invalidate the grant of clemency or for Congress to impose limits on the exercise of the presidential pardon power.

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