Michigan courts are arguing over one of those gray areas.
A police officer comes into your home to check on you, but then finds something illegal and charges you with a crime.
That happened to a man in Hazel Park.
According to the Associated Press, police came to check on Eric Hill after a neighbor told police Hill had not been seen for several days and his cats were looking out the window.
Once inside, police discovered marijuana growing in his closet and charged him with drug crimes.
The Fourth Amendment protects you against "unreasonable search and seizures."
But what's "unreasonable"?
Today, the Michigan appeals court answered that question in the case against Eric Hill. The three-judge panel reversed an Oakland County judge's ruling and reinstated the case against Hill.
In its 2-1 decision, the appeals court said there would have been a "community uproar" if Hill needed medical attention and officers didn't enter in March 2010.
The dissenting judge, Jane Markey, said there's no evidence that Hill was in immediate need of help, and she called the police work "sloppy."