"Kill them without a trial. Just a bullet in the head and say goodbye. Why waste taxpayer money?" said Thomas Pland, 70, a truck driver from Astoria, Queens.
"If they want me to do it," he added, "I will."
Mike Keane, owner of O'Hara's Restaurant & Pub a block from Ground Zero, said: "They should have taken care of them in Guantanamo Bay. Hang them there. It would have been quicker and easier."
Families of 9/11 victims slammed the White House for affording the mass murderers the same legal rights as Americans, instead of prosecuting them as foreign enemies in military tribunals.
"I'm a hundred thousand percent against this move. They're war criminals!" said retired firefighter Joe Holland, whose son, Joseph III, a commodities trader, died in the World Trade Center's north tower.
"This is crazy. This is insane. They're going to make a mockery of the whole court system 10 blocks away from the World Trade Center. They're going to scream for holy war in America."
Peter Gadiel, head of 9/11 Families for a Secure America, fumed, "I never thought we could have gotten a worse president than George Bush. But we got one.
"The president wants a circus? He should hold the trial in Lafayette Park at the White House. That makes as much sense," added Gadiel, whose son, James, a Cantor Fitzgerald employee, died on 9/11.
Debra Burlingame, whose brother Charles was piloting one of the hijacked jets, called the upcoming trials in the city a "travesty."
"This is going to make us look like fools in the Muslim world," she said.
But retired firefighter James Riches, whose firefighter son, Jimmy, died on 9/11, said he would give President Obama the benefit of the doubt -- for now.
"Hopefully, we're doing the right thing. But if this all goes awry, I'm going to hold Obama and his Justice Department responsible," Riches said.
Views were mixed among downtown workers.
Katelyn Collins, a 24-year-old legal assistant from Brooklyn, said: "I want to see justice firsthand. I pass Ground Zero every day and see the destruction -- a giant hole in the ground."
"I will believe until the day I die that Sept. 11 was an act of war and not just another criminal act," former Mayor Rudy Giuliani said. "This confirms my worst expectations for the Obama administration, that they would be in denial with regard to the danger of Islamic terrorism."
Rep. Peter King (R-LI) said, "This is as bad of a decision as any president has ever made."
But Rep. Jerrold Nadler (D-Manhattan), whose district includes Ground Zero, said trying the 9/11 plotters near the scene of the crime is poetic justice.
"New York is not afraid of terrorists, we want to confront them, we want to bring them to justice, and we want to hold them accountable for their despicable actions."