A "Postal" Review
Pros:
-It certainly gets its point across.
-If a trespasser's lawyer were to try to point out that the prosecution had not posted a sign properly, this sign would remove all doubt.
-If, and I reiterate IF, this sign is a parody trying to show that putting the word "Posted" at the top of a posted sign is a ridiculous waste of space, then well done.
Cons:
-Self-destructively self-referencing. 'Nuff said.
Verdict: I deem this sign to be postable, but only in special situations. Use judgment accordingly.