Equal protection of the law is guaranteed by the 5th and 14th Amendments to the U.S. Constitution. Generally speaking, equal protection means that a person should be treated the same under the law as others who are similarly situated, unless there's a legally sufficient reason to treat the person differently.
In the simplest terms, equal protection of the law is all about how the government classifies us. Equal protection classifications fall into three broad categories.
- Non-suspect classifications. Classifications that don't raise concerns about unfair discrimination are considered non-suspect. The government can use non-suspect classifications as long as they're rationally related to meeting a legitimate government interest.
- Suspect classifications. Classifications based on characteristics like race and ethnicity, national origin, and (when done by states) lack of citizenship are called suspect classifications. To use a suspect classification, the government must show that the classification is the least restrictive means to achieve a compelling government interest.
- Quasi-suspect classifications. Classifications based on gender and illegitimacy are considered quasi-suspect. If the government wants to use one of these classifications, it must show that the classification is substantially related to achieving an important government interest.