Shaneen Allen faces three and a half years in prison because she made an honest mistake, followed by a mistake of honesty. Allen, a 27-year-old phlebotomist who lives in Philadelphia, drove to Atlantic City with a gun in her purse, erroneously thinking her Pennsylvania carry permit would be respected in New Jersey. Then she told a state trooper about the gun when he pulled her over for a traffic violation.

Last week a state judge refused to dismiss the resulting charges against Allen, a single mother of two with no criminal record, or to order that prosecutors approve her participation in a pretrial diversion program. Her trial, scheduled for October 6, will pit New Jersey's draconian gun laws against compassion and common sense.

Last year Allen, after being robbed twice, legally bought a .380-caliber Bersa Thunder pistol for personal protection. She had owned it just a week when she was pulled over for an unsafe lane change on the Atlantic City Expressway around 1 a.m. on October 1.

Allen, who was on her way to an Atlantic City hotel to prepare for her son's birthday party a few days later, followed the standard advice for people with carry permits who are stopped by police. She volunteered that she had a gun in the car and showed the state trooper her permit as well as her driver's license.

Allen did not realize that her carry permit, unlike her driver's license, was no good in New Jersey. Although Pennsylvania's carry permits are recognized by 29 other states, New Jersey is not one of them.

New Jersey not only does not recognize other states' carry permits; it is stingy with its own. They are reserved for people who can demonstrate what police officials consider a "justifiable need." Under a policy that has been upheld by state courts, that means "persons specifically employed in security work" or "others who can establish an urgent necessity."

You may wonder how that policy, which gives the government nearly unfettered discretion to decide who may exercise the constitutional right to bear arms, comports with the Second Amendment. It doesn't, although last year the U.S. Court of Appeals for the 3rd Circuit somehow managed to conclude that it does.

In any case, Shaneen Allen was not trying to test New Jersey's laws when she crossed the border with a handgun in her purse. It is plain from the way she got caught that she did not realize she was breaking the law.

But as Nicola Bocour of Ceasefire NJ told the Associated Press, "ignorance is no excuse for not knowing the law." Probably she meant that ignorance is no excuse for breaking the law. You get the idea.

Another gun control activist, Bryan Miller of the Philadelphia-based group Heeding God's Call, argues in a recent op-ed piece published by the Cherry Hill Courier-Post that Allen's prosecution will improve public safety by discouraging Pennsylvania permit holders from carrying their guns over the Delaware River—as if New Jersey has seen a wave of violent crimes committed by law-abiding gun owners like Allen. Atlantic County Assistant Prosecutor Deborah Hay likewise cites "deterrence" as a reason to pursue the case.

What about justice? If convicted Allen faces a mandatory minimum sentence of three and a half years. The maximum, taking into account an additional charge for possessing hollow-point ammunition, is more than 11 years.

"Mistakes happen," Allen told Fox News. "I just hope that everything turns out OK for me and my kids, because I'm all they have."

As Allen's attorney, Evan Nappen, explained after last week's hearing, "she really has nothing to lose by going to trial at this point," since the only plea bargain offered by prosecutors would require Allen to serve three and half years (i.e., the mandatory minimum). It looks like her fate will be determined by a jury's willingness to do the right thing, which in this case means ignoring an unjust law.