Three and a half years ago, in the aftermath of the horrific massacre of children and staff at Sandy Hook Elementary School in Connecticut, advocates thought the stage was set for major national gun control legislation.

Nothing happened.

Now, following the mass shooting in Orlando, Florida — the deadliest in U.S. history — President Barack Obama, Hillary Clinton and others are calling for a ban on assault weapons of the type used in the nightclub attack and Sandy Hook.

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Yet, as the nation reels from another in a long list of shooting massacres in the past decade, experts and advocates disagree on what, if anything can be done to stop them.

Short of federal legislation, which he said will not happen, at least in the short term, the slaughter of innocents will continue, said Robert Spitzer, a professor of political science at SUNY Cortland and the author of “Guns Across America,” which chronicles the history of gun laws in the United States.

Congress “will not only do nothing, it’s not going to talk about this because they have no desire to even debate the issue, to hold hearings, much less to consider legislation,” Spitzer said.

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A proponent of stricter gun control laws, Spitzer said Republicans control both houses of Congress and “want no part of any measures that might strengthen guns laws and will be very happy when the issue goes away and dies down, as it sooner or later will.”

Other experts such as James B. Jacobs, a professor of constitutional law and the courts at New York University, and Randy Barnett, a professor of legal theory at Georgetown University Law Center, who both are skeptical of gun control laws, also believe little will shift nationally.

The Orlando shooting, which claimed the lives of 49 victims, “won’t change anything,” Jacobs said. “Sandy Hook didn’t change anything. People called me all the time after Sandy Hook and said ‘surely the murder of six- and seven-year-old children, this has got to be it.’ ”

“Until we have a new president and a new Congress, there is no possibility of major gun control legislation,” Jacobs said.

Orlando now sits at the top of a dubious list that includes Sandy Hook and eight other mass shootings in the past decade:

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  • A holiday party for county workers in San Bernardino in December 2015
  • A community college in Oregon in October 2015
  • A church in South Carolina in June 2015
  • A naval installation in Washington D.C. in September 2013
  • A movie theater in Colorado in July 2012
  • An immigration center in upstate Binghamton in April 2009
  • A military base in Texas in November 2009
  • A university campus in Virginia in April 2007
  • Of those shootings, only the church massacre in South Carolina that claimed the lives of 9 victims, is not among the 10 deadliest mass shootings in U.S. history.
  • Like he has done after other massacres since he took office, Obama mourned the victims of the latest carnage Sunday in an address to the nation.
  • “We have to decide if that’s the kind of country we want to be,” Obama said. “And to actively do nothing is a decision, as well.”
  • Gun rights advocates led by the National Rifle Association contend the right to bear arms is enshrined in the Second Amendment, and that if more civilians had guns they might have been able to defend themselves in places such as the gay night club in Orlando.
  • People inside the club were not allowed to have weapons due to a Florida law.
  • “It took SWAT three hours to breach that hall” in Orlando, Barnett of Georgetown said.
  • The people inside “would have had a chance” if they were armed, Barnett said. “There’s no guarantee. But if you are completely defenseless against an armed individual then there is a pretty good chance you are going to lose.”
  • Spitzer said arming the population even more that it already is — there are some 300 million weapons in a nation of 320 million people — is not likely to deter mass shootings.
  • “The idea that civilian amateurs carrying handguns would be helpful I think is vastly outweighed by the fact that it is a lot more likely” they would make a mistake and “accidentally shoot somebody who was innocent . . . or would use them in an encounter between individuals that escalates quickly and where tempers get out of control,” he said.
  • The NRA declined to comment. In a newspaper Op-Ed this week, Chris W. Cox, the executive director of the group’s Institute for Legislative Action, said the problem is not guns but allowing terrorists and criminals to get their hands on them.
  • “Law-abiding gun owners are tired of being blamed for the acts of madmen and terrorists,” Cox wrote. He noted that anti-assault rifle laws in California and other gun bans in Brussels and Paris did not stop terrorist attacks there.
  • Some gun rights advocates and experts believe there simply is no solution to mass shootings in a country where the right to bear arms is embedded in the Constitution.
  • “I don’t think there is a solution,” Jacobs said. “If there was one, we would have come up with it.”
  • He said with so many firearms owned by private citizens, “the train has left the station. There is no way of getting those guns out of the hands of the civilian population. It’s too late.”
  • Gun control advocates disagree. They say state laws passed in New York, Connecticut and other locations since Sandy Hook have had an impact in those areas. Orlando could push the movement nationwide.
  • “On a federal level this could potentially be a tide change,” said Emily Sussman of the left-leaning think tank Center for American Progress in Washington, D.C. “I think we have to build on the progress that started after Sandy Hook. It was never going to be overnight. And people are just incredibly fed up with the lack of action.”
  • Allison Anderman of the San Francisco-based Law Center to Prevent Gun Violence said states such as New York have led the way in showing mass shootings can be deterred. The 2013 SAFE Act has an extensive background check mechanism and limits the amount of ammunition assault rifles can use, for instance.
  • “We know that 90 percent of Americans support universal background check laws yet many of their legislators fail to vote in favor of these types of laws because they are beholden to the gun lobby,” Anderman said. “We have an epidemic of gun violence in the U.S. that is unparalleled in the developed world and we need to do the things that are going to address that epidemic.”