WASHINGTON -- Americans have given up a lot in the name of increased security. Intrusive and expensive measures adopted since 9/11 have eroded privacy, made air travel arduous, and turned public buildings into bunkers -- at a cost of something like a half-trillion dollars.

But when it comes to individual rights or reasonable expectations that Congress considers negotiable in the pursuit of safety, the ability to purchase military-level firepower seems off the table.

"There is something wrong when one person can get pulled aside at the airport because he left a couple of paper clips in his pocket, while someone else can buy thousands of rounds of ammunition online without anyone noticing," said Marc Rotenberg, executive director of the Electronic Privacy Information Center, a civil libertarian group.

Thanks to devoted lobbying by the National Rifle Association, and the Republican Party's use of guns as a highly politicized wedge issue, even the feeblest attempts at restricting weaponry are dead on arrival in Washington.

The very idea of banning military-style assault weapons or high-capacity magazines -- such as the ones used in the Aurora, Colo., Batman shooting on Friday -- is way more politically fraught than, say, letting the government secretly spy on citizens without a warrant.

Even people on the U.S. government's terror watch list can still buy guns, thanks to the GOP.

In contrast, many of the steps taken by the Department of Homeland Security -- and particularly its Transportation Security Administration -- have been widely criticized as ineffective.

Forcing air passengers to take off their shoes, for instance, is "based on securing a particular tactic, when switching tactics is easy," said Bruce Schneier, a private security technologist and author. "The next guy put the bomb in his underwear," he noted.

One team of economists calculated that onerous security screening has led more people to drive in cars rather than deal with airports, resulting in some 500 more traffic deaths annually.

Airport security measures "make it marginally harder for terrorists to go in and blow up a plane in flight," said Charles Perrow, a Yale University sociology professor emeritus who has called the creation of DHS "The Disaster After 9/11". "But we have very few of those incidents, compared to what we spend to prevent them. The response is totally inappropriate.

"We lose 11,000 people a year from weapons. We lose practically zero a year from terrorist attacks," Perrow said.

Meanwhile, as far as Perrow is concerned, there's no real cost associated with banning weapons that have no practical purpose other than mass shooting.

So technically, that's an infinite cost-to-benefit ratio. "You don't get that very often," Perrow said.

Restricting military-style weapons sales certainly has common sense going for it. "It seems pretty obvious to me and a lot of other people, if you don't allow people to buy this stuff, they can't use this stuff," Schneier said.

"But in this country, you cannot have a rational security debate that involves guns," Schneier said. "The politics is so great that any analysis is ignored by half the population."

Perrow said President Barack Obama missed a key opportunity a few months into office when he failed to support a Democratic bill that would have reinstated a ban on assault weapons that the Bush administration let expire.

"I just think that was cowardice on Obama's part," Perrow said.

Ohio State University professor John Mueller wrote in a recent book that DHS focuses way too much attention on terrorist attacks and way too little on common occurrences.

Those include such things as hurricanes, tornadoes -- and mass shootings.

Mueller's estimate of a half-trillion dollars in federal spending for increased security is only the half of it. He and his coauthor estimate that when you add private sector costs and "opportunity costs" of delays and inconveniences, the increased spending in the U.S. exceeds $1 trillion.

Such enhanced expenditures would be cost-effective only if a 9/11-scale attack would have occurred more than once a year without them, they concluded.

"What people have given up is some degree of privacy, and convenience, and obviously tax money," Mueller told HuffPost. "That's a lot of money."

Meanwhile, shootings involving high-powered weapons, high-capacity magazines and multiple victims have become nearly commonplace. The Brady Campaign to Prevent Gun Violence maintains a list of mass shootings since 2005 that is 62 pages long -- and counting.

Loading Slideshow...
  • 1981: The Attempted Assassination Of President Ronald Reagan

    on March 30, 1981, President Reagan and three others were shot and wounded in an assassination attempt by John Hinckley, Jr. outside the Washington Hilton Hotel in Washington, D.C. Reagan's press secretary, Jim Brady, was shot in the head.

  • 1993: The Brady Handgun Violence Act

    The Brady Handgun Violence Act of 1993, signed into law by President Bill Clinton, mandated that federally licensed dealers complete comprehensive background checks on individuals before selling them a gun. The legislation was named for James Brady, who was shot during an attempted assassination of President Ronald Reagan in 1981.

  • 1994: The Violent Crime Control and Law Enforcement Act

    The Violent Crime Control and Law Enforcement Act, signed into law by President Bill Clinton in 1994, instituted a ban on 19 kinds of assault weapons, including Uzis and AK-47s. The crime bill also banned the possession of magazines holding more than ten rounds of ammunition. (An exemption was made for weapons and magazines manufactured prior to the ban.)

  • 2004: Law Banning Magazines Holding More Than Ten Rounds Of Ammunition Expires

    In 2004, ten years after it first became law, Congress allowed a provision banning possession of magazines holding more than ten rounds of ammunition to expire through a sunset provision. Brady Campaign President Paul Helmke told HuffPost that the expiration of this provision meant that Rep. Gabby Giffords's alleged shooter was able to fire off 20-plus shots without reloading (under the former law he would have had only ten).

  • 2007: The U.S. Court of Appeals For The District Of Columbia Rules In Favor Of Dick Heller

    In 2007 The U.S. Court of Appeals for the District of Columbia ruled to allow Dick Heller, a licensed District police officer, to keep a handgun in his home in Washington, D.C. Following that ruling, the defendants petitioned the U.S. Supreme Court to hear the case.

  • 2008: The NICS Improvement Amendments Act

    Following the deadly shooting at Virginia Tech University, Congress passed legislation to require states provide data on mentally unsound individuals to the National Instant Criminal Background Check System, with the aim of halting gun purchases by the mentally ill, and others prohibited from possessing firearms. The bill was signed into law by President George W. Bush in January of 2008.

  • 2008: Supreme Court Strikes Down D.C. Handgun Ban As Unconstitutional

    In June of 2008, the United States Supreme Court upheld the verdict of a lower court ruling the D.C. handgun ban unconstitutional in the landmark case <em>District of Columbia v. Heller</em>.

  • Gabrielle Giffords And Trayvon Martin Shootings

    Gun control advocates had high hopes that reform efforts would have increased momentum in the wake of two tragic events that rocked the nation. In January of 2011, Jared Loughner opened fire at an event held by Rep. Gabrielle Giffords (D-Ariz.), killing six and injuring 13, including the congresswoman. Resulting attempts to push gun control legislation <a href="http://www.huffingtonpost.com/2012/04/09/trayvon-martin-shooting-gun-debate_n_1413115.html" target="_hplink">proved fruitless</a>, with neither proposal even succeeding in gaining a single GOP co-sponsor. More than a year after that shooting, Florida teenager Trayvon Martin was <a href="http://www.huffingtonpost.com/news/trayvon-martin" target="_hplink">gunned down</a> by George Zimmerman in an event that some believed would bring increased scrutiny on the nation's Stand Your Ground laws. While there has been increasing discussion over the nature of those statutes, lawmakers were <a href="http://www.huffingtonpost.com/2012/04/09/trayvon-martin-shooting-gun-debate_n_1413115.html" target="_hplink">quick to concede</a> that they had little faith the event would effectively spur gun control legislation, thanks largely to the National Rifle Association's vast lobbying power. Read more <a href="http://www.huffingtonpost.com/2012/04/09/trayvon-martin-shooting-gun-debate_n_1413115.html" target="_hplink">here</a>:

  • Colorado Movie Theater Shooting

    In July of 2012, a heavily armed gunman <a href="http://www.huffingtonpost.com/2012/07/20/aurora-shooting-movie-theater-batman_n_1688547.html" target="_hplink">opened fire on theatergoers</a> attending a midnight premiere of the final film of the latest Batman trilogy, killing 12 and wounding scores more. The suspect, James Eagan Holmes, allegedly carried out the act with a number of handguns, as well as an AR-15 assault rifle with a 100-round drum magazine. Some lawmakers used the incident, which took place in a state with some of the laxest gun control laws, to bring forth legislation designed to place increased regulations on access to such weapons, but many observers, citing previous experience, were <a href="http://www.huffingtonpost.com/2012/07/20/batman-shooting_n_1690547.html" target="_hplink">hesitant to say</a> that they would be able to overcome the power of the National Rifle Association and Washington gun lobby.