Suppose that Bob, with no justification, draws a gun¹ and aims it at Bill. This gun is illegal to possess in their jurisdiction. Bill, who was unarmed initially, manages to overpower Bob and take the gun before Bob can fire it.

  1. Has Bill committed a crime by possessing the gun?
  2. If (a) Bob still poses an immediate threat (perhaps he has another gun), or if (b) another person threatens him², is Bill allowed to use the gun that he took from Bob in self-defense?

¹ If the answer would clearly be the same if "gun" were replaced with "knife" or another weapon, that would be worth noting, but I'm primarily interested in how the situation applies to guns.

² In both (a) and (b), assume that Bill would certainly be allowed to use deadly force if he had already been legally carrying a weapon prior to the incident.

  • Of course the answer to number 1 is "no, it's legal," so I assume you're actually asking which aspects of the law lead to this conclusion for any juridiction -- is that right
    – phoog
    Commented Jan 31 at 7:33
  • 22
    Consider that the alternative would imply that a criminal could make themselves impossible to legally disarm simply by carrying an illegal weapon. It would also imply that people should determine the legality of their assailant's choice of weapon before acting in self-defense. Commented Jan 31 at 14:02
  • 54
    @Lag : This is a good example why it's better to stick to Alice and Bob. Both because it's easier to tell them apart than Bill and Bob, and because we can use pronouns throughout the text without ambiguity as an additional descriptor.
    – vsz
    Commented Jan 31 at 15:27
  • 7
    @NuclearHoagie it wouldn't be the first time laws have had unintentional consequences
    – Aubreal
    Commented Jan 31 at 19:37
  • 1
    @stackoverblown there's no government on Mars or Venus yet, so the answer for both of those places is that it's legal by default. In the US, it is legal as explained in Therac's answer. As for your island, feel free to post an answer saying what your law on the topic is!
    – Someone
    Commented Feb 1 at 20:12

5 Answers 5


It's legal to take an attacker's gun, and use it in self-defense, until you reach the police.

The legality of using a gun in self-defense is not dependent on whether you're allowed to carry a gun, or this particular gun, in peaceful circumstances. Holding the firearm against the immediate threat (Bob) would fall under temporary lawful possession, or innocent possession defense.

[a] person has innocent possession of a weapon when [that person] comes into possession of the weapon in an excusable manner and maintains possession, or intends to maintain possession, of the weapon only long enough to dispose of it safely (CJI2d[NY] Temporary and Lawful Possession).

Discharging the firearm in public is allowed for self-defense (typical statute), so no offense there. Assaulting the attacker to take the gun is also covered under self-defense.

Other criminal actions required for legal self-defense, but not covered by self-defense, would generally be covered under the necessity defense.For instance, destruction of property - breaking the assailant's gun, or damaging property while firing it in self-defense - would be protected by necessity.

Holding on to the gun to use it in self-defense some other day would be illegal possession. If you find yourself in a situation of predictable danger, your expected actions are to reach safety as soon as possible. Basically, you're allowed to keep the gun until police arrives, or on your way to the police.

Ultimately, whether the weapon is found fortuitously or obtained by disarming an attacker, the underlying purpose of the charge is to foster a civic duty on the part of citizens to surrender dangerous weapons to the police.

  • 9
    Of course if you own an illegal gun, then using it in self defense would be legal (but a judge might be look very very hard at your claim of self defense), but your gun ownership would still be a crime.
    – gnasher729
    Commented Jan 31 at 10:27
  • 4
    @gnasher729: Depending on the situation; I see a plausible case of necessity defense for having the illegal gun in the first place, with the need of a gun being already in evidence.
    – Joshua
    Commented Jan 31 at 18:44
  • 5
    "The legality of using a gun in self-defense is not dependent on whether you're allowed to carry a gun" a famous example of this was Wisconsin Rittenhouse case, where he was charged with both homicide and illegal possession of a firearm. It was possible that he could be found innocent of the major charges while being found guilty of possession (though they dropped that charge before the trial was decided).
    – eps
    Commented Jan 31 at 21:23

You have asked many questions on this site about whether it can be self-defence to do X. The answer is always the same: any offence may be justified or excused by self-defence or defence of another.

The defences of "self-defence" and "defence of another" are available defences to any act that would otherwise constitute "an offence" in Canada. Section 34 simply says: "A person is not guilty of an offence if... [and then goes on to list the elements of the defence]."

Your question seems to ask about the scope of actions that might be justified or excused by the defence.

If it wasn't clear before 2012, amendments in 2012 to the self-defence laws in Canada made it absolutely clear that any offence may be justified or excused by self-defence or defence of another. As the Supreme Court describes in R. v. Khill, 2021 SCC 37:

The accused’s response under the new law is also no longer limited to a defensive use of force. It can apply to other classes of offences, including acts that tread upon the rights of innocent third parties, such as theft, breaking and entering or dangerous driving.

The substantive elements of self-defence and defence of another are described several other Q&As, so I will only state them briefly: (a) reasonable belief of a threat of force; (b) the act constituting the offence is for the purpose of protection; (c) the act committed is reasonable. For details see:

  • 12
    Upvoted for the opening sentence alone. (but the rest is good too...) Commented Jan 31 at 16:59
  • 6
    The query subject/title tells the start of a story that people want to hear. Basically clickbait that hits the HNQ list and up goes the querant's rep ¯\_(ツ)_/¯. Maybe they're writing a book.. who knows the motivation .. Commented Jan 31 at 22:17

While possession of certain guns (especially fully automatic ones) is illegal per se, and Bill might not be allowed to possess any gun for lack of a license, Bill is acting in self-defense. Self-defense allows one to break other laws without punishment within the area that is deemed proportional and required to avert the harm.

Taking an illegal weapon for it was the only means of preventing your death or someone else's death is proportional, even if possession of the gun would be a crime in itself.

Similarly, if the situation of self-defense continues and is not escalated by Bill, then even the use of the illegal weapon can be absolved, as long as Bill isn't the one that escalates.

However, Bill can not retain the weapon after the situation of self defense is over: if Bob runs, Bill can't keep the gun. However, the laws allow the surrender of a found or otherwise acquired weapon to the police. In the circumstances of 'I took this weapon of my assailant', those facts together with surrendering it for confiscation would prevent possession charges.


Given the circumstances, it seems highly unlikely that Bill would be prosecuted under any law for briefly holding the gun. (Of course, it would be another matter if he subsequently kept the gun.)

If he were investigated or prosecuted for an offence related to holding the gun, the defence of necessity is available as a general defence. Bob may say that, given the circumstances, it was justifiably necessary to commit the offence because of the consequences to him if he hadn't (his serious injury or death, caused by Bob).

A common example is two mountain-climbers joined by rope, one of them falls and the other is put in the position of having to choose between (a) cutting the rope to save herself thereby killing her companion or (b) to die with her companion.

To paraphrase R v Conway [1989] Q.B. 290:

the defendant was constrained by circumstances to do as he did to avoid death or serious bodily harm to himself.


Real world example.
Sample size of one.
It may depend where you are. I'm in NZ.
In August 2022 I disarmed a knife wielding attacker who was attacking pedestrians. Possession of a knife of the size involved in public is an offence.

The police said that when they watched the video (local Town Hall entrance ) they were impressed.
The regional police commander made favourable comment to the local news media.

I conclude that the police consider my possession of the knife legitimate :-)

  • the taking and securing of it.
    – Trish
    Commented Feb 3 at 1:50
  • @Trish I don't know where the term "securing" came from - it's not mentioned above. Does this look secured enough? (That's my good eye - I was fortunate. Commented Feb 4 at 11:28
  • "Not in an assailant's hands" is secured usually
    – Trish
    Commented Feb 4 at 11:55
  • 2
    @trish So, being in mine qualifies :-) . Commented Feb 4 at 14:30

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .