This isn't like a drivers licensee where we can just allow a carry over between states because to do otherwise would just be wildly impractical. These are lethal weapons that have been heavily debated for years and years. Different states have different laws because we as a nation do not agree with what the standards should be. If the state you are entering has tighter control laws, it is reflective of the people who live there. They don't want weapons being carried around or they simply want more protections in place. When you enter a persons home, you should respect their rules. When you enter their state it should be the same. Someone here said something to the effect of, "Criminals carry guns across borders, why shouldn't law-abiding citizens?" Because they are law-abiding. And justifying actions by putting criminals up as the example has never been a strong argument. If you want to carry a gun in a state that won't let you, move there and take part in their state wide discussion on the subject.