The laws on whether or not it's legal to shoot trespassers vary greatly depending on what state you're in. Generally speaking, there are certain circumstances where an occupant may be able to legally shoot trespassers.
But the legality of pulling the trigger depends on so many circumstances that dialing 911 may be a safer bet.
In general, property owners cannot use deadly force to protect property. But property owners may be able to shoot at trespassers in self-defense if they fear great bodily harm or death.
The law gives property owners the right to defend themselves with a reasonable response. That means any force used against a trespasser must usually be proportionate to harm that is reasonably perceived.
The legality of shooting a trespasser will further depend on whether you have a duty to retreat or a right to stand your ground, and the extent of your curtilage (your property surrounding your home) that counts as your dwelling.
For example, Florida lets you open fire on someone forcibly trying to enter your dwelling -- including your attached porch -- but not the rest of your property (such as a yard).
Also, since most state laws require that a trespasser knowingly or intentionally enter someone's private property, it's important for property owners to have a "No Trespassers" sign in place to serve as notice.
But remember, shooting at a trespasser is always a legal gamble. The legality of such actions is incredibly state-specific and fact-specific. Property owners could potentially be held liable -- civilly and/or criminally -- if their efforts cross the line.
Call the Police
To avoid any legal ambiguity, property owners may want to use other ways to keep trespassers away. If the measures are too little too late and an uninvited guest makes an appearance on your property, call the police.
Although it might be more difficult to get a quick response in more rural areas, having the police investigate relieves homeowners of many of the risks and liabilities of taking aim at trespassers themselves.