Yes. Although Tae Kwon Do skills take longer to attain than it would take to acquire a gun, knife or club, they relieve one of the necessities of carrying anything at all. Also, your hands and feet are legal, you need no permit to carry them. Below are several examples of how you might use Tae Kwon Do for self-defense.
The student of the martial arts attains confidence in his ability to control and protect himself. A calm, confident person is less likely to be attacked to begin with.
If someone should grab hold of you, there are many break-hold techniques. Calmly assess the situation and decide which technique best first the circumstances, then use it – quickly and decisively. (Tae Kwon Do practice helps one learn to avoid panic.)
Blocking techniques enable one to stop or dodge a blow from a fist, foot club, knife or even a gun (provided the assailant is within striking range – even Tae Kwon Do cannot make you bulletproof).
Tae Kwon Do training also includes knowledge of the human anatomy. Various points of the body are extremely vulnerable, and a blow to one of them can be fatal. A blow to certain other points can break, paralyze or cause such severe pain as to disable an attacker. In the event that you have no choice but to strike another person, it is up to you to decide how much damage is necessary. Part of the philosophy of Tae Kwon Do is to do as little harm as possible. Therefore, although it may be necessary in some instances, do not strike to kill unless you have no viable alternative. If you harm another person, once you are certain they are no longer a threat, you should render any first aid or life-supporting help you are capable of. The ideal situation would be, if possible, to discourage the other person by demonstrating your technique on some inanimate object, or by striking him in such a way that you cause him pain but no real damage.