A foot-high electric fence. Seems the commonest approach around here (western Oregon) for racoons that get in fish ponds anyway. Doesn't need much charge to discourage them, and you can just step over it.
Now if you had a deer problem it would be more of a challenge. I know of one case where a buck liked grapes so much that he would just bull his way past an electric fence to get in. A hunter friend of mine with a night scope, and a special "nuisiance animal" permit obtained by the the vinyard owner, ended this career of crime. It amazed me the the the buck would just push right by the wire, getting zapped the whole time, to get in.
--arne