The Supreme Court ruled in the 2008 case D.C. v. Heller that the Second Amendment protects an individual right to possess weapons—or at least commonly used weapons—in the home. In 2010's McDonald v. Chicago, the Court found that states and localities were also barred from violating that right. But those landmark rulings left unsettled a host of important questions about how, when, and why the government can regulate or restrict gun rights.

"The Second Amendment right is not unlimited," Justice Antonin Scalia cautioned in the majority opinion in Heller. "It is not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose." For example: "concealed weapons prohibitions have been upheld under the Amendment or state analogues. The Court's opinion should not be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms."

The Supreme Court hasn't taken up any new Second Amendment cases since McDonald, but that doesn't indicate a lack of interest. The Court receives thousands of petitions for review—or certiorari—each year, but it replies to only a few hundred. It has recently plucked a handful of Second Amendment cases from the submissions pile, asking for responses from the relevant parties.

"The fact that the Supreme Court has been requesting responses," lawyer C.D. Michel wrote at calgunlaws.com in February 2012, "shows the Justices are paying unusually close attention to the Second Amendment issue." Michel went on to theorize that "the Court is interested in further clarifying the scope of Second Amendment rights but is searching for the right case vehicle to do so." Meanwhile, other cases are percolating through the lower courts that may soon end up getting SCOTUS' attention.

Here are five important cases that could expand Second Amendment liberty and clarify some of the core issues left unresolved by Heller and McDonald. The cases involve who can legally obtain weapons, what kinds of weapons they can own, how they can use them, and where they can use them. Two of them have filed certiorari petitions with the Supreme Court, though whether they'll be taken up remains to be seen.

NRA v. BATFE

This case is about who can legally obtain guns. It challenges the 1968 federal prohibition on licensed gun dealers selling handguns or handgun ammo to adults between the ages of 18 and 20. People in that age range can buy long guns, such as rifles or shotguns, and they can legally possess handguns. But they are barred from purchasing any of these items from licensed dealers, restricting their ability to obtain what they are permitted to own.

The case has dragged on since 2011, necessitating the addition of a new plaintiff (since the original pair of complainants have reached age 21). Two lower courts considering the case decided that 18- to 20-year-olds have no rights under the Second Amendment, never mind Heller.

The petition for certiorari requests the Supreme Court to decide "whether a nationwide, class-based, categorical ban on meaningful access to the quintessential means to exercise the right to keep and bear arms for self-defense can be reconciled with the Second Amendment." That question has potential relevance beyond the age cohort at issue: There are legal limits imposed on the gun rights of convicted felons and those adjudicated mentally ill, for example.

The lower courts' opinions in NRA v. BATFE show they are not taking the Second Amendment very seriously. The U.S. District Court for the Northern District of Texas, which initially granted the government's request to dismiss the case in September 2011, thought that since "Congress identified a legitimate state interest-public safety-and passed legislation that is rationally related to addressing that issue," neither the Second Amendment nor equal protection of the law mattered. The court's reasoning went like this: Congress did it, they thought they had their reasons, that settles it.

A panel of the Fifth Circuit Court of Appeals then decided that the Second Amendment didn't really have bearing on this case. Why? Certain types of people had been barred from gun ownership even back in the Founding era. Additionally, in the 19th and 20th centuries various laws prevented minors from owning weapons when the age of majority was still 21. (In the Founding era, though, 18- to 20-year-olds were part of the armed militia.)

The Fifth Circuit also seemed to invent a new comparative responsibility doctrine for applying full constitutional rights. The Second Amendment, the judges found, only "protects 'law-abiding, responsible' Citizens." And "Congress found that persons under 21 tend to be relatively irresponsible."

In a failed attempt to get the Fifth Circuit to rehear the case en banc, a dissent from Judge Edith Jones in the 8-7 vote wondered when else courts would ever decide that a constitutional right did not apply to "a law-abiding adult class of citizens," mocking the decision's extremely weak version of "intermediate scrutiny," its basis for determining whether the government's restriction furthers an important state interest in a directly relevant way.

The Supreme Court has not defined what level of judicial scrutiny should apply to Second Amendment cases. It has rejected as a guideline mere "interest balancing," in which a court decides whether the benefits of a given restriction outweigh its costs to the citizen. Same with a "rational basis review," in which the government merely has to prove that the rights-restriction is rationally related to furthering some state goal.

Lower court application of "intermediate scrutiny" to Second Amendment cases has curtailed the expansion of gun rights in many post-Heller cases. Alan Gura, the lawyer who won both Heller and McDonald before the Supreme Court, says that the doctrine here "is not the intermediate scrutiny that's usually applied in constitutional cases, such as gender-based discrimination under the Equal Protection Clause." Under real intermediate scrutiny, Gura contends, "post-hoc rationalizations are insufficient, and the government bears the burden of showing a substantial fit between an important interest and the regulation at issue." Yet under Second Amendment intermediate scrutiny as applied by lower courts, "the legislative excuses or police declarations are given presumptive weight, and the burden is laid upon the challengers. Sometimes the government is required to come back with more evidence, but this appears to largely be a pro forma step. Most (but not all) laws survive this analysis."

The Supreme Court is expected to hold a hearing on whether to take on NRA v. BATFE in late February.

Drake v. Jerejian

This case is about where you can have and use your gun. First filed in November 2010, it challenges New Jersey's Handgun Permit Law, which says that carrying in public without a permit can get you 5 to 10 years in prison.

The law has been upheld so far by both the U.S. District Court for the District of New Jersey and the Third Circuit Court of Appeals. The plaintiffs argue that the law is an unconstitutional prior restraint on their Second Amendment rights, since it requires a potential gun carrier to prove to the police a "justifiable need" involving specific previous threats before they can get a carry permit. And that's hard to do-around 1,200 such permits are extant in the state now, out of an adult population of 6.7 million.

Plaintiff John Drake restocks ATMs for a living, and thinks that he might at some point need a gun in public. Another plaintiff is a sheriff's deputy who according to the state magically loses his ability to safely use a gun in public when he goes off duty.

The Third Circuit decision by Judge Ruggero Aldisert declares baldly that "the requirement that applicants demonstrate a 'justifiable need' to publicly carry a handgun for self-defense qualifies as a 'presumptively lawful,' 'longstanding' regulation and therefore does not burden conduct within the scope of the Second Amendment's guarantee." Whether that restriction is lawful after Heller is exactly what's at issue—surely some longstanding "presumptively lawful" gun restrictions are now not lawful in the wake of that decision. Merely presuming it is without argument is brazen.

Aldisert's decision was based on taking government claims on faith. "The predictive judgment of New Jersey's legislators," he wrote, "is that limiting the issuance of permits to carry a handgun in public to only those who can show a 'justifiable need' will further its substantial interest in public safety." How do we know it would? Aldisert admits that "New Jersey has not presented us with much evidence to show how or why its legislators arrived at this predictive judgment."

No evidence? No problem. "As the District Court correctly concluded, New Jersey's legislature 'has continually made the reasonable inference that given the obviously dangerous and deadly nature of handguns, requiring a showing of particularized need for a permit to carry one publicly serves the State's interests in public safety.'" That supposed "reasonable inference" is all the judge needed to bar a vast number of New Jerseyans from tools of self-defense they might need outside their home.

The plaintiffs filed for certiorari to the Supreme Court in early January. The petition points out that the issue of carry permits is ripe for Supreme Court consideration; "the federal appellate courts, and state courts of last resort, are split on the question of whether the Second Amendment secures a right to carry handguns outside the home for self-defense. The Second, Fourth, Fifth, and Seventh Circuits, and the supreme courts of Illinois, Idaho, Oregon, and Georgia have held or assumed" that citizens do have that right; but both the Third Circuit in this case, and "the highest courts of Massachusetts, Maryland, and the District of Columbia" think that public carry can be far more circumscribed legally.

The cert petition gets to the heart of the problem with the Third Circuit decision: "Until now, even courts applying a highly deferential 'intermediate' scrutiny standard in Second Amendment cases have at least required the government to point to some legislative findings or other evidentiary support justifying the burdening of this fundamental right," the plaintiffs note. "The majority [in the Third Circuit] excused the complete absence of legislative finding and evidence supporting the challenged provision because the legislature was unaware that individuals enjoy Second Amendment rights. It is difficult to imagine what constitutional right could survive the logic employed."

Cooke v. Hickenlooper

This case is about the size of magazine you can legally insert into your gun. Last year Colorado banned any newly purchased magazines that can hold more than 15 rounds. (Older 15+ magazines are grandfathered in.) The law was signed by Gov. John Hickenlooper in March. In May, this federal lawsuit, with 55 state sheriffs among the plaintiffs, challenged the law in U.S. District Court in Colorado.

David Kopel, a Second Amendment scholar and lawyer for the sheriffs (and a bevy of other plaintiffs) summed up the suit's goals in a July press release: "The Heller decision forbids bans on arms which are 'Typically possessed by law-abiding citizens for lawful purposes.' We will show magazines of up to 20 rounds for handguns, and up to 30 rounds for rifles, are standard for many popular firearms, and thus protected under Heller."

Given that there had never previously been any documentation requirement for the private or retail purchase of magazines, it would be quite an investigative challenge for any sheriff to distinguish a forbidden new one from a permitted old one; some sheriffs involved in the suit have publically announced they don't intend to try to enforce the magazine ban.

A 2011 decision from the Court of Appeals for the District of Columbia upheld an even narrower magazine restriction than this Colorado one: a ban on magazines holding more than 10 rounds. That case was known as Heller II since it featured the same parties as the original 2008 D.C. v. Heller case. Heller II challenged some of the gun regulations D.C. adopted after the city's total ban on handguns was overturned.

The decision, by Judge Douglas H. Ginsburg, claimed that the D.C. magazine ban does not substantially burden the core self-defense right embedded in the Second Amendment. "The Government has the burden of showing there is a substantial relationship or reasonable 'fit' between, on the one hand, the prohibition on magazines holding more than ten rounds," Ginsburg wrote, "and, on the other, its important interests in protecting police officers and controlling crime." The judge deemed the government to have met that burden, basically because larger magazines would allow mass shooters-who account for a statistically insignificant percentage of actual users of larger magazines-to do more damage and harm more people.

The left-wing publication Mother Jones found 31 such mass-murderous uses of high capacity magazines, out of an estimated 40 million in circulation. Like the definition of "assault rifle," the definition of "high-capacity magazine" in lawmakers' eyes is arbitrary, unpredictable, and ignores the size that particular gun manufacturers intended for their weapon.

Why does anyone need a "high-capacity" magazine, however a legislator wants to define it? Well, why does anyone need an Xbox, or any specific type of food, soap, or car? It's a product that exists in the world, and in the overwhelmingly huge percentage of the time, people use it for pleasure with zero harm to anyone else. Reloading your weapon during your legitimate peaceful use of it can be aggravating. If larger capacity magazines exist, innocent, peaceful gun users will want to use them.

Small victories have already arisen from this suit. The law's original language banned any magazine "designed to be readily converted" to the illegal capacity, which could include any magazine with a removable base plate. Colorado's attorney general has since agreed that the ban would only apply to magazines that had actually been converted. A trial to settle the rest of the case is currently scheduled to begin at the end of March.

Wilson v. Cook County

This case is about the kinds of weapons you can own. In 2007, a trio of plaintiffs sued Cook County, Illinois (where Chicago is located), over a 2006 law banning certain types of guns and ammunition that the county deemed "assault weapons." The ordinance included no grandfather clause for those who thought they had been obeying the law up until now: They had 90 days to surrender the weapons, take them out of the county, or modify them to match the law's requirements. Punishment for noncompliance was up to six months in prison or a $500-$1,000 fine.

The plaintiffs believe that the Cook County definition of "assault weapon" is so arbitrary and confusing (containing as it does the usual bunch of cosmetic features with little connection to the "danger" of a weapon) that the law should be considered unconstitutionally vague. They also argue that barring citizens from owning such a wide variety of previously legal weapons violated the Second Amendment.

Before the McDonald decision, two lower state courts wanted to toss the Wilson case. While it was on appeal to the Illinois Supreme Court, McDonald was handed down, establishing that localities had to obey the holding in Heller. The Illinois Supreme Court then sent the case back to a lower appeals court to reconsider, and that court still held that the assault weapons restrictions didn't violate the Second Amendment, since the ban was, as the state Supreme Court later summed it up, "supported by the historical tradition of prohibiting the carrying of dangerous and unusual weapons and allow[ed] for the continued protected use of common firearms."

In its April 2012 decision, the Illinois Supreme Court found that the definition of the qualities that make for an illegal assault weapon were laid out clearly enough to avoid unconstitutional vagueness. On the Second Amendment question specifically, jurists thought there was enough doubt about whether the weapons barred by the law should be considered commonly used weapons good for self-defense in the home that they remanded consideration of the core question back to the lower courts.

The plaintiffs are now working their way back up to the Illinois Supreme Court. A decisive victory against barring widely used weapons for arbitrary reasons would go a long way toward cementing Second Amendment rights nationwide.

New York State Rifle and Pistol Association v. City of New York

This case is not likely to be fast-tracked to the Supreme Court. But its existence tellingly (and maddeningly) demonstrates the picayune restrictions on a core constitutional right that localities still indulge in after Heller—even when the laws in question will reduce the safety of citizen gun ownership, in this case by making gun training and practice more difficult.

New York City has on the books Title 38, which prohibits licensed handgun owners from taking guns almost anywhere outside of city limits. You cannot take your gun to your second home outside the city; you cannot take your gun to shooting practice outside the city; you can only travel with your gun within the state upon receiving a separate hunting permit. In the city, you can only take it to the shooting range, and there's only one shooting range within city limits. It has a waiting list of around five days.

The individual plaintiffs in the case were prevented from attending out-of-state shooting competitions because of Title 38. Preventing a permit-holding citizen from practicing and competing in shooting proficiency, the suit argues, furthers no substantial government interest.

A decision on a motion for a preliminary injunction against enforcing the restriction had been stayed awaiting final resolution of a somewhat similar case, Osterweil v. Bartlett, currently at the Second Circuit Court of Appeals. Alfred Osterweil had challenged New York's denial of his gun license after he informed the city that his New York address was no longer his primary residence but just a vacation home. A district court, again applying "intermediate scrutiny," determined that the law could stand, since demanding that licensees have a primary domicile in New York suits the state's need "to monitor its licensees more closely and better ensure the public safety."

The Second Circuit in Osterweil asked the New York State Court of Appeals whether it considers "an applicant who owns a part-time residence in New York but makes his permanent domicile elsewhere eligible for a New York handgun license in the city or county where his part-time residence is located?" In October, that state appeals court said someone would indeed be eligible for a weapons license in his or her part-time residence in New York.

A sensible decision. The U.S. District Court for the Southern District of New York should follow the spirit of that reasoning and apply it to this case. In doing so, it should overturn Title 38, recognizing that permission to use a legally owned gun should not be restricted to specific domiciles or to the borders of a certain city.

The prohibitions being challenged in all five of these cases infringe on individual freedom while likely failing to prevent any harm. They represent lawmaker prejudice against weapons and their owners, not the reasoned pursuit of an actual civic good.

Most Americans understand that these sorts of laws are pointless. That's why, despite a recent string of tragic news stories about people using weapons to injure or kill, 63 percent of respondents in a December Reason/Rupe poll recognized that tougher laws aren't going to effectively prevent criminals from accessing weapons. Governments on all levels should take the hint: Stop wasting their time, and our money, trying to defend these pointless provisions in court.