In the process of making laws, legislatures sometimes establish classifications that give one group an advantage over another. For instance, in the United States those under the age of 21 are not allowed to purchase alcohol. This rule shows preference to the group of individuals who are 21 and older.

Certain laws which advantage one group over the other can be contentious and may eventually be appealed to a high court.

In United States Supreme Court jurisprudence, strict or intermediate scrutiny is applied to regulations which affect groups that fall under a "suspect classification". Rational basis scrutiny is applied to non-suspect classifications. The Supreme Court Building, Washington, D.C. The Supreme Court Building, Washington, D.C., (large image) The Supreme Court of the United States, located in Washington, D.C., is the highest court (see supreme court) in the United States; that is, it has ultimate judicial authority within the United States... Jurisprudence is the theory and philosophy of law. ... Rational basis review, in U.S. constitutional law, is the lowest level of scrutiny applied by courts deciding constitutional issues through judicial review. ...

To be considered a suspect classification in the U.S. a group must meet all of the following criteria:

1. The groups' characteristics are immutable. (Race, national origin)
2. The group shares a history of discrimination.
3. The group is politically impotent.

4. The group is a distinct and insular minority.

Suspect classifications which discriminate on the basis of race or national origin are typically analyzed under strict scrutiny. Gender classifications receive heightened or intermediate scrutiny. Strict scrutiny is the highest standard of judicial review used by courts in the United States. ... Intermediate scrutiny, in U.S. constitutional law, is the middle level of scrutiny applied by courts deciding constitutional issues through judicial review. ...