[nolemmings]

while the word verbal might literally mean by the use of words, the term is superfluous when used as it was by Leon. Of course a warning here would be through the use of words, unless he intended that he was sending the offender symbols, gestures, smoke signals, a one-act mime play, etc. Thus, Mirriam-Webster definition #3 for verbal, i.e. "3 : spoken rather than written", applies and was not truly intended by the speaker, making it incorrect, IMHO.

Respectfully,
The Knights Who Say Ni