On the wall of the National Rifle Association headquarters in Fairfax, Virginia, a phrase—or part of one—is emblazoned in oversized lettering: “..the right of the people to keep and bear arms, shall not be infringed.” The part before the dot-dot is one of the big questions Michael Waldman explores in The Second Amendment: A Biography, a revealing new history of one of the more contentious and misunderstood provisions of the U.S. Constitution.

“If you read James Madison’s notes from the Constitutional Convention and the Constitution itself,” Waldman says, “the Founders were very focused on the states keeping strong militias—who would lead the militias, how would they be armed, could the federal government take them over—and above all, they did not want a standing army. They thought a standing army could be tyranny and that the answer was to have state militias.”

Waldman is a legal scholar and president of the Brennan Center for Justice at the New York University School of Law, a nonpartisan think tank that focuses on public policy issues like redistricting, voting rights and privacy.

The full Second Amendment—including the prefatory part about militias—states: “A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed.” Waldman says there’s no evidence in the historical record that the Founders debated whether the Constitution should protect an individual’s right to keep firearms; the discussion, rather, was always about militias.

“If you look at the notes from the Constitutional Convention, from the debates on the House floor when they marked up the Second Amendment, the transcripts of the ratifying conventions, it was overwhelmingly about the militias,” Waldman says. “That doesn’t mean they didn’t think people shouldn’t protect themselves; they just didn’t think it should be in the Constitution.”

And until recently, the Supreme Court didn’t think so either. In District of Columbia v. Heller (2008), the Supreme Court struck down a law that banned handguns in the District of Columbia on the basis that an individual has a constitutional right under the Second Amendment to possess a firearm regardless of whether the firearm is for participation in a militia. Until Heller, the Supreme Court had never recognized an individual right to firearms.

Waldman says the decision in Heller was no fluke; it was the end product of a long, patient, concerted effort by firearm activists to change a longstanding view of what the Second Amendment means.

“The NRA and its allies were effective over three decades in putting forth the view that the Second Amendment gives an individual right. They started with scholarship, they moved to change public opinion, then moved to change the positions of government agencies,” Waldman says. “Only then did they go to court. By the time they got to the Supreme Court, the ruling fell like a ripe apple. There’s some real lessons in there about how social change—legal change—happens in America.”

Heller is one of a handful of decisions in recent years that shows the Supreme Court moving in a decidedly conservative direction, including Citizens United v. FEC (2010)and McCutcheon v. FEC (2014), which loosened campaign finance restrictions; Shelby County v. Holder (2013), which struck down a portion of the Voting Rights Act; and the recent Schuette v. Coalition to Defend Affirmative Action (2014), which upheld a law limiting consideration of race in college admissions.

“The Roberts Court has been very activist in using its interpretation of rights to strike down laws—many of them longstanding and many of them democratically formed,” Waldman says. “Heller was the first major case where the Roberts Court moved to the right, but it was far from the last. Citizens United, Shelby County, and the near decision to strike down the Affordable Care Act based on an originalist idea of what the Constitution meant could all be seen as activist.”

The sin of judicial activism, i.e., “legislating from the bench,” is largely in the eye of the beholder. In the 1930s, a conservative Supreme Court struck down many of FDR’s New Deal laws, and progressives called for judicial restraint. In the 1950s and ‘60s, the progressive Warren Court expanded privacy rights, criminal rights, and reproductive rights, and conservatives called for judicial restraint. In the present Roberts Court era, the finger-pointers have again switched sides.

“Now you’ve got a very conservative court, and a lot of liberals are rediscovering the virtue of judicial restraint,” Waldman says. “We’re used to the people decrying judicial overreach as being conservatives, but these days it’s more likely to be the liberals.”

Waldman says many new firearms cases are already moving through the courts. The constitutionality of restrictions on concealed-carry laws, magazine-clip laws, etc., depends a lot on whether and when some of these cases reach the Supreme Court. As conservatives hold only a 5-4 majority, replacing even one of the justices with a more progressive jurist would change the outcome in many close cases.

“The whole issue of guns in America has become a constitutional crusade,” Waldman says. “Politicians say, ‘I am a strong supporter of the Second Amendment.’ We are still having a debate over what that means.”

Scott Porch is an attorney and writer in Savannah, Georgia. He writes frequently about books for Kirkus Reviews, Salon.com, and Huffington Post, and he is writing a book about social upheaval in the 1960s and '70s.