Hard cases make bad law is an adage or legal maxim meaning that an extreme case is a poor basis for a general law that would cover a wider range of less extreme cases. In other words, a general law is better drafted for the average circumstance as this will be more common.[1]
The original meaning of the phrase concerned cases in which the law had a hard impact on some person whose situation aroused sympathy.[2]
The expression dates at least to 1837. It was used in 1904 by US Supreme Court Justice Oliver Wendell Holmes Jr. Its validity has since been questioned and dissenting variations include the phrase "Bad law makes hard cases", and even its opposite, "Hard cases make good law".