ONE question that worries many visitors to defensivecarry.com, a website devoted to the delights and pitfalls of life with a hidden gun, is whether their “concealed-carry” permits will be valid outside the state in which they are issued. Can they take their guns on holiday with them? Can they pack them in their checked bags for a flight? What if their plane is diverted to a spot like New York, which makes it exceedingly difficult to carry a gun? And if they cannot bring their guns with them, how will they defend themselves and their loved ones when threatened?

Gun-rights activists have a simple solution: require all states to honour one another's concealed-carry permits. There is no reason to suppose, says Andrew Arulanandam of the National Rifle Association (NRA), that a person considered fit to carry a gun in one state would suddenly become a menace to society on entering another. Many states already have such reciprocal agreements, without any obvious ill effects, he adds. The House of Representatives agrees: earlier this month it approved a bill that would make one state's permit valid in any other, with the exception of Illinois and the District of Columbia, both of which do not allow concealed weapons at all.

Opponents of the measure, including the mayors and police chiefs of many big cities, say it will allow people to get around local rules about who can obtain a concealed-weapon permit. Many states require permit-holders to undergo safety training, for example, or deny permits to alcoholics; others do not. Four states—Alaska, Arizona, Vermont and Wyoming—do not require a permit at all, although three of them do helpfully issue them for use outside the state. The question of which states have the cheapest and easiest-to-obtain permits is another popular topic on defensivecarry.com. Forcing states to accept the permits of the most permissive jurisdictions would be an assault on states' rights, says Mark Glaze of Mayors Against Illegal Guns, a pressure group.

It will fall to the Senate to adjudicate. John Thune, a Republican from South Dakota, says he is working on getting concealed carry through the chamber. He was also the leader of the last attempt, in 2009, that fell just two votes short of approval. Conditions look more favourable now. Several of the Democrats who voted against reciprocity then have since been replaced by Republicans, who tend to be keener on gun rights. Others, such as Claire McCaskill of Missouri, are facing difficult re-election battles in gun-friendly states. Even Barack Obama, the bogeyman of gun-rights groups, has wavered on the subject of concealed carry. He claimed to oppose it as a candidate, but then signed a law permitting it in national parks in 2009.

Mr Obama, facing a difficult re-election battle of his own, would probably prefer not to offend anyone by weighing in on either side this time. Harry Reid, the leader of the Democratic majority in the Senate, could well grant him his wish, by preventing the subject from coming to a vote. And even if there is a vote, gun-control advocates assume that when the chips are down enough Democrats would probably be available to foil Mr Thune again. But relying on allies who do not wish to come forward until the last minute is always a nerve-racking proposition.