"The law is made up of rules and standards.
Here is an example of a rule, established by the Supreme Court in Roper v. Simmons in 2005: If you commit murder even hours before your 18th birthday, you cannot be put to death for your crime. The same killing a few hours later may be a capital offense. The court drew a bright-line rule at 18..." Adam Liptak, New York Times, "Sidebar - Bright Lines Blur in Juvenile Sentencing" (November 23, 2009)