I am not a lawyer. The following information was culled from other sources and is provided for the convenience of my readers. It is your responsibility to know and obey the law.
State firearm laws vary considerably. Some states have almost none, like Vermont. Others have pages and pages, like Massachusetts.
It is important not to confuse firearm law with self defense law.
Firearm law covers the buying, selling, possession, and carrying of firearms.
Self defense law covers when, where, and how the use of force and deadly force is justified.
Alaska, Arizona, Kansas, Maine and Vermont allow permitless concealed carry by anyone not prohibited from possessing a gun. You must be 21 or older and have an ID.
D.C. and Illinois have recently been forced by court decisions to allow concealed carry, but they make it hard.
The other 44 states require a permit for concealed carry, but many allow permitless open carry.
Some states require a permit for open and concealed carry.
Some states do not allow open carry. Texas is a "must conceal" state.
Most states have restrictions on where you can carry. Restricted places often include government buildings, police stations, schools, bars, airports, and churches. (Federal buildings, including post offices, are restricted by federal law.)
Some states require you to inform police if you are carrying a firearm any time you have "contact"; for example you get stopped for speeding.
Many states issue "non-resident" licenses. In other words they will issue a license to someone who does not live in their state.
Some states recognize licenses or permits from other states. Some do not. Some will only recognize a license from another state if you live in that other state. In other words they do not recognize non-resident licenses.
Florida and Utah are the most recognized licenses.
Follow the links below to learn about the states you live in or visit. Don't neglect to read the info (laws, FAQs) published by the state itself, or consult a lawyer in that state.
Some good info on state law.
Handgun Law US http://www.handgunlaw.us/
NRA gun laws http://www.nraila.org/gun-laws.aspx
If you are the biggest, baddest lion on the African plain you can strut around killing anything and everything that seems even remotely threatening. Right or wrong, nobody will challenge you until the day when a bigger, badder lion shows up and sends you to that big Serengeti in the sky.
Living in a civilized society has its pluses and minuses, but if you look at the big picture there are way more pluses.
Civilized society arrays itself against the bad guys, thereby keeping their numbers in check. Most of the time you can count on the system to help you lead a safe, peaceful and uneventful life.
Occasionally you will face the bad guy alone. The problem is, that often only the bad guy knows for sure that there is a bad guy and that it's him. The bad guy has an advantage because he can act, while the good guy must react.
Also there are two sides to every story. The bad guy will lie if he has to. Civilized society will not know who to believe. Civilized society will not tolerate you making Swiss cheese out of someone because he might have been a threat to you.
Every state in the US allows you to answer deadly force with deadly force, but it might not be obvious to civilized society that the bad guy is the bad guy, or that he was prepared to use deadly force against you.
So what is my point? Before you get in a situation where you have to decide whether to use deadly force or not you should answer this question:
Am I prepared to spend the rest of my life in prison and/or lose everything I own, to save my life or the life of someone else?
The chances that you will be prosecuted for defending yourself with deadly force depend on many factors:
Be aware that if you are involved in any deadly force incident that does not take place inside your home, you will most likely be arrested. Remember that the police don't know that you are the good guy.
Being arrested does not mean you will be prosecuted. Being prosecuted does not mean you will be convicted. But plenty of good guys get in a heap of trouble employing armed defense.
Talk to your lawyer before you talk to the police.
Bottom line: Don't shoot anybody unless it is probable that what the bad guy is going to do to you (rape, murder, permanent injury) is worse than what society may do to you (jail, loss of assets) if you fail to convince them you were justified.
Do not use deadly force to prevent the loss of property. It is not allowed in most states, and in any event the wheelbarrows full of money you pay your lawyer to keep you out of jail would replace the property many times over. This is what insurance is for.
Caution! In many states displaying a gun is considered deadly force even if you don't fire it!
If you are serious about staying on the right side of the law, get a copy of "Self-Defense Laws Of All 50 States" by Mitch and Evan Vilos. It contains a very thorough discussion of the concepts of justified self defense, the actual laws of all 50 states, actual jury instructions and outcomes of several cases, and lots of practical advice on staying on the sunny side of the bars.