Maybe we are going about this wrong

 http://www.huffingtonpost.com/2013/03/08/whole-foods-gmo-labeling-2018_n_2837754.html

 With the news this week that Whole Foods will have all products labelled for GMO's by 2018 it seems that the tide is turning. But why does it seem so difficult to get this onto the product?

It seems there is a big push to have genetically altered foods labelled. There is a growing demand for it. But we all know the big corps are totally against it. We know why. They want to put as much cheap crap as they can in anything so they can make bigger profits and they don't want you to know about. They have every incentive in the world to stop this from happening.
In the past, we saw this resistance with the zero calories claim, the trans fat claims, the sugar free claims and all sorts of deceptive labeling that they got away with for as long as they could.
Last week when I was in the grocery store, I noticed just how small they make the list of ingredients. It is surely because they are required to put them there but don't want you to see them. If you did, you might notice something like this:

http://blog.medfriendly.com/2011/11/does-your-kids-cereal-contain-bht-or_7163.html 

My take on this:
It is going to be very tough to get them to label these products. The easier way would be to get those products that don't have any GMO's in them to label that they are GMO free. In that way, the resistors are outed by not labelling and then will be forced to either remove the GMO's or admit that they have them.
This works exactly the way the trans fat free labelling works now. When you see any product, if it doesn't say it is trans fat free then you know it has trans fat. Because that is a big selling point, it becomes an advantage to have that as a selling point. Once people begin to notice non GMO labelling they will ask questions. At first directly to the grocer and companies, but then just generally they might do some research to see why and what it all means. 
You go shopping and if it doesn't say it is GMO free then you assume it has them. Seems to me the easiest way to get what we want. And we don't need any government approval for it. 
When big corps try to be deceptive the only way you beat them is to outsmart them and show them they will lose money.
Just like any other instance money and profit are the determining factor. Take away market share and companies will come back in line and they will be lining up to label their products or ditch the GMO's if necessary.