"Personally I believe that patenting genes in first place is overall a bad idea..."

If they actually developed the genes themselves, I'd lean towards the thought that they should be patentable.

However, in this case (and in every case that I know of involving Monsanto) they've simply patented something they discovered, not something they invented.

The gene in this case is the "Roundup Ready" gene... which comes from a bacteria they discovered that was living in the soil they saturated with their Roundup poisons. They extracted this gene and inserted it into the plant by way of a virus... so they didn't invent the insertion method either (the virus did). Yes, they had a guiding hand in which gene got transferred, but that's process and that's not what they're suing over.

In other cases, they simply patented genes that they never even interacted with, such as the large hog gene. This is fundamentally broken... I'm not sure what happened to the rules against patenting nature/life.

As to the merits of this case, I can see it going either way - the arguments are definitely novel.

Personally, I think:

1. Patentability of discoveries (not inventions) should be examined closely (and discarded!). There used to be rules against patenting nature/life... as stated above, I'm not sure what happened to those (IA-quite-obviously-NAL).

2. SCOTUS should consider that Monsanto sells a product that is intended to be used to replicate itself - then suing people who use the end product as nature intended for further replication. Consider if this were a seed that produced a seedless fruit... you'd have to be a bit more creative than following nature to replicate the plant (grafting and such). That effort wasn't applied here at all.

3. SCOTUS should examine the fact that Monsanto has completely lost control of their product and that it should be viewed as an infection.

To elaborate on that last point, imagine you're an organic farmer and you go through an extreme amount of effort and cost to ensure you have truly organic seed. You plant this seed on your land that has been organic for >3 years (requirement for getting a USDA Organic label, as I understand it) and grow your crop. Bees come to gather nectar and in doing so, pollinate your crop (nature at work). Unfortunately, there's another farm within range of the bees that has Monsanto's crop growing, and your crop gets fertilized with the neighbor's pollen. The product of your hard work now contains Monsanto's genes, they come on your property without your permission, take parts of your crop for analysis, then 2 years later (ensuring you have no proof to fight it) they launch a lawsuit against you claiming you stole their product and sue you into bankruptcy. EDIT: Not only have you lost your current crop and your money, but you've also lost your organic label since you now have a non-organic crop growing in your fields (even though the non-organic part is only the product of the plant and not the plant itself).

This is not a theoretical possibility, this is their MO.
They're wiping out all sources (crop-reuse methods, included) of seed so all farmers will be forced to buy seed from them (they also control the majority of non-GMO seed, they've been buying up smaller seed companies for eons).

Edited for formatting and added one line to the 2nd-to-the-last paragraph.