While attention is focused on the U.S. Senate, which could begin voting as early as next month on gun control legislation, some state lawmakers are trying to move in the opposite direction.

Bills to nullify any gun control measures that Congress enacts have been introduced in at least 36 states since the beginning of the year, according to an analysis using Scout, the Sunlight Foundation's legislative alert system. To browse the list and click through to the text of the bills, click here.

Whatever likelihood of passage -- or of surviving a constitutional challenge -- the measures demonstrate the strength of the backlash against the movement for gun control that followed last December's schoolhouse massacre in Newtown, Conn. It also underscores the clout wielded in state legislatures by anti-gun control organizations such as the National Rifle Association and Gun Owners of America.

Congress is debating a number of gun regulations, including broader and tougher background checks for gun buyers, a ban on assault weapons -- now considered unlikely to pass -- and a ban on high-capacity magazines that were used in recent mass shootings at Newtown, Aurora, Colo, Tucson, Ariz. Debate in the Senate could begin as early as April 8, and gun control advocates are ramping up public pressure as evidenced by the ad above, part of a $12 million campaign underwritten by New York City's independently wealthy mayor, Michael Bloomberg.

The states where nullification bills have been introduced range from Republican strongholds like Alabama to Democratic territory such as Maryland and Oregon. The bills run the gamut from resolutions defending the Second Amendment to laws that would penalize officials for enforcing federal gun control laws. A number preemptively target proposed gun measures currently before Congress, barring the enforcement of federal gun regulations enacted after the first of this year. Others are more general and conceivably could contradict laws currently on the books.

Many of these bills declare that federal firearms laws do not apply to the state in question, something that is "flagrantly unconstitutional," according to Harvard University constitutional law professor Laurence Tribe.

"Article VI of the Constitution establishes the supremacy of federal over state law. The Second Amendment creates no exception. We fought a Civil War that settled the matter in blood as well as ink," Tribe wrote in an email.

Nonetheless, measures stipulating that state firearm laws supersede any conflicting federal measures have passed state Houses in UtahWyoming and Alaska, Those measures also bar any state and federal officer from enforcing federal gun laws.

In some states, legislators appear to be trying to out-do each other in their zeal to oppose federal gun control. At least 15 nullification bills were introduced in Mississippi -- though none made it out of committee, according to the Law Center to Prevent Gun Violence and Sunlight's Scout tracker. At least nine gun control nullification bills have been introduced in Kentucky and Tennessee. The legislatures of Texas, Missouri and Tennessee each have at least five nullification bills under consideration.

Even in Colorado, where Democratic Gov. John Hickenlooper last week signed landmark legislation to limit the size of gun magazines and require universal background checks for gun buyers, bills were earlier introduced in the House and Senate terming any federal restriction on magazine size unenforceable.

Wyoming's law gets specific, saying that any federal "law, rule, or regulation" created after January 1, 2013 to ban certain guns, limit magazine capacity or require gun registration is unenforceable.

Other lawmakers are pushing what appear to be more symbolic measures against Washington regulation. Virginia Republican Senator Thomas Garrett, Jr.'s resolution, signed by the Senate and House, is short and sweet, saying that the Supreme Court "has found that the Second Amendment protects the right of individuals to possess any bearable arm commonly used for lawful purposes."

But Virginia's House of Delegates steered clear of the more radical course chosen by Wyoming, Utah and Alaska's Houses. A bill sponsored by Del. Robert Marshall, R-Va., would have made it illegal to assist the federal government in enforcing any new firearm regulation. Nearly two thirds of the House rejected it in January.

In Arizona, senators wrote a resolution that is essentially a list of talking points against gun control, claiming that Americans are safer today than at any time since the 1960s, and that Roman and Grecian philosophers viewed self-defense as an inalienable right.

As it is early in the legislative season, most of the nullification bills have only been introduced. It's yet to be seen if many of them will make headway, let alone be signed into law. The list of states where we have found them is below. Know of any we're missing? Email us.

  • Alabama
  • Alaska
  • Arizona
  • Arkansas
  • Colorado
  • Georgia
  • Idaho
  • Illinois
  • Indiana
  • Iowa
  • Kansas
  • Kentucky
  • Maine
  • Maryland
  • Michigan
  • Minnesota
  • Mississippi
  • Missouri
  • Montana
  • Nebraska
  • New Hampshire
  • New Mexico
  • North Dakota
  • Oklahoma
  • Oregon
  • Pennsylvania
  • South Carolina
  • South Dakota
  • Tennessee
  • Texas
  • Utah
  • Vermont
  • Virginia
  • Washington
  • West Virginia
  • Wyoming