Merriam-Webster's Word of the Day for January 07, 2009 is:

sanction • \SANK-shun\  • verb
1 : to make valid or binding usually by a formal procedure (as ratification) *2 : to give effective or authoritative approval or consent to

Example sentence:
The parks committee was willing to sanction the consumption but not the sale of alcohol on park premises.

Did you know?
"Sanction" can also be a noun meaning "authoritative approval" or "a coercive measure." The noun entered English first, in the 15th century, and originally referred to a formal decree, especially an ecclesiastical decree. (The Latin "sancire," meaning "to make holy," is an ancestor.) By the end of the 17th century, the meaning of the noun "sanction" had extended to refer to both a means of enforcing a law (a sense that in the 20th century we began using especially for economic penalties against nations violating international law) and the process of formally approving or ratifying a law. When the verb "sanction" appeared in the 18th century, it had to do with ratifying laws as well. Soon it had also acquired an additional, looser sense: "to approve."

*Indicates the sense illustrated in the example sentence.