My wife was driving on the 417 yesterday and went the wrong direction. This portion the exits are farther apart than normal. She say a portion to do a U turn and looked for a sign and didn't see one, so she did a U turn to head back the other way.

The officer pulled her over some time after and said that she didn't obey the sign, and she said she didn't see a no U-turn sign and that is why she did it. He said, it didn't matter because everyone knows that those are for emergency vehicles only. So he gave her a ticket for failing to obey signs. I went to google earth and sure enough there is no sign about U-turn or emergency vehicles only. Would I be able to fight this ticket?

Here is the picture. My question is how can you get a ticket for failing to disobey a sign, if there isn't one there?

I think you are right but there are a lot of things you can get a ticket for without a sign being present. He should have given a ticket for driving on the shoulder.

Sounds like you have a decent argument for getting this dropped but you will need some evidence that the sign isn't there. I would go back ASAP and see if you can get your own photo showing that there is no sign as the court won't except a Google Maps print out as evidence. There is a good thread on this site about getting pictures admitted as evidence that would be worth reading.