Sanction

Well how on Earth has this escaped my attention for 26 years?!

sanc·tion (s ngk sh n)
n.
1. Authoritative permission or approval that makes a course of action valid. See Synonyms at permission.
2. Support or encouragement, as from public opinion or established custom.
3. A consideration, influence, or principle that dictates an ethical choice.
4.
a. A law or decree.
b. The penalty for noncompliance specified in a law or decree.
5. A penalty, specified or in the form of moral pressure, that acts to ensure compliance or conformity.
6. A coercive measure adopted usually by several nations acting together against a nation violating international law.

tr.v. sanc·tioned, sanc·tion·ing, sanc·tions
1. To give official authorization or approval to: "The president, we are told, has sanctioned greed at the cost of compassion" David Rankin.
2. To encourage or tolerate by indicating approval. See Synonyms at approve.
3. To penalize, especially for violating a moral principle or international law.
[Middle English, enactment of a law, from Old French, ecclesiastical decree, from Latin s ncti , s ncti n-, binding law, penal sanction, from s nctus, holy; see sanctify.]
sanc tion·a·ble adj.

Word History: Occasionally, a word can have contradictory meanings. Such a case is represented by sanction, which can mean both "to allow, encourage" and "to punish so as to deter." It is a borrowing from the Latin word s ncti , meaning "a law or decree that is sacred or inviolable." In English, the word is first recorded in the mid-1500s in the meaning "law, decree," but not long after, in about 1635, it refers to "the penalty enacted to cause one to obey a law or decree." Thus from the beginning two fundamental notions of law were wrapped up in it: law as something that permits or approves and law that forbids by punishing. From the noun, a verb sanction was created in the 18th century meaning "to allow by law," but it wasn't until the second half of the 20th century that it began to mean "to punish (for breaking a law)." English has a few other words that can refer to opposites, such as the verbs dust (meaning both "to remove dust from" and "to put dust on") and trim (meaning both "to cut something away" and "to add something as an ornament").