Much of the argument that people will be disarmed of their weapons and have those weapons used against them stems from a long history of police officers being shot with their own firearms. To combat this problem law enforcement has adopted various handgun retention systems.
While the private citizen carrying a concealed firearm isn’t as likely to be a target for a disarm while the firearm is holstered, I can certainly see a number of scenarios where an assailant might make an attempt against a drawn gun.
If a criminal doesn’t believe that you are going to shoot, or is willing to risk a bullet to escape arrest they might decide to try to do a disarm.
Get good equipment. I frequently see $1000 guns in $20 holsters, worn on $2 belts. A good holster and a belt are a significant portion of the holstered retention equation. Cheap holsters will not keep the gun from falling out, or will rip right off of the belt leaving the attachment loops behind. Holsters that snap or clip onto the belt offer almost no resistance. I highly recommend purchasing high quality holsters, and belts. While much more expensive they truly do last much longer so the expense is justified in the long run.
Use good ready positions. Some ready positions lend themselves to gun grabs more readily than others. The weaker the position the more inviting it is for a grab. The classic low-ready (arms extended at about a 45 degree angle) is one of the worst for both shooting and retention. Keeping the firearm tucked against the body is the mechanically strongest un-holstered position.
Don’t use the wrong tactics. People that want to hold the assailant at gun point until the police arrive expose themselves to a greater risk of disarm attempts. The time spent in proximity to the criminal is a window of opportunity for something to go wrong. Complicating that with trying to dial 911 and communicate with the dispatcher creates a distraction that most people could do without. It would be better to get a good description and have them run and then call the police after they have left. The legal justification for using your firearm is a threat to your life, the subject’s non-compliance may or may not constitute a threat that you can justify shooting him for. It would be much better for us if we didn’t have to shoot anyone.
You can’t always ‘Just shoot’ them. A common answer to people grabbing for an un-holstered handgun is to shoot the person making the grab, but this isn’t always as simple as it sounds. If the assailant has a hold on the gun it can retard the action of the slide (or bind the cylinder on a revolver) preventing more than one round from firing. When the gun discharges it might not be oriented toward the assailant, so gambling on the ‘one shot stop’ is even less of a good bet.
There is also whole class of gun-grabbers that we don’t want to shoot. It might be a friend or spouse who thinks you are over-reacting, it might be the 70 year old grandmother of the assailant who just wants to protect their grandchild. We might be able to make the argument that shooting this class of people is legally justified by the circumstances but again, it would be preferable not to have to do so.
Martial arts or combatives might help you. These can fulfill at least part of the role of retaining the gun. The problem is that a lot of martial arts are largely incompatible for fighting with a drawn gun. Whatever arts or techniques you intend to apply must maintain control of the muzzle and be aware that this fight is going to take place in a clinch. If you need distance to execute your technique you are probably not going to get it. Losing control of the firearm generally means that you are now in the position of needing to perform a disarm in order to ultimately retain the gun. Disarming techniques are part of retention.
Don’t abandon the gun. I have seen it advocated to let go of the gun, and either transition to another weapon or apply combatives or martial arts techniques to recover it. It would never be my primary plan to loose physical control of the gun. At best such a strategy provides the assailant with a club, and at worst a fully functioning firearm.
Transition to another weapon. I am all for transitioning to another weapon if it is available, but I would keep control of the primary whenever possible. In such a situation I would prefer a knife to a backup firearm. A few good cuts should produce some psychological and mechanical advantage.
