This could come down to wording. There are instances where companies have gotten into trouble for intentionally taking steps in one product line to favor another product line or for having a very large market share in one product line and using that to potentially stymie competition in another product line. A quick example would be Microsoft a few years ago when the EU sued them saying that Microsoft was using the "Windows Platform" business to favor their "applications" business (word, excel, Explorer, etc) and prevent fair competition.
https://en.wikipedia.org/wiki/Microsoft_Corp._v._Commission
So "obligated to allow"...Agreed that Canon does not have to do something like share their protocols. At least, not yet, read to the bottom of the Microsoft situation, the EU is insisting upon for Microsoft to make changes to promote competition but their market share is larger than Canon's. But they certainly should not do something that intentionally inhibits the ability of a 3rd party lens to be used on their bodies.
A quick example, if Canon added code that turned the camera off if a non-canon lens was mounted....that would be anti-competitive.
As for companies suing Canon...sure they would, or at least file a complaint. Yelp and others have filed a complaint against Google/Alphabet. I've heard of complaints against Amazon. Microsoft is routinely in these situations. Corporations have legal departments for a reason.
I think I mostly agree with this...sure they have a right to protect their intellectual property. Also, they are not obligated to share proprietary information. But, that isn't really what I meant. If there are complexities in Canon's new codes that truly have a purpose that benefits the camera system, that is fine. If it makes it very difficult for 3rd party lens manufacturers, that is fine too (too an extent). But, if Canon takes steps to intentionally thwart the use of a third party lens, or if it is decided Canon has a monopoly or near monopoly in camera bodies and that monopoly unfairly favors the sale of their lenses/thwarts competition...well, that changes things.
As to if Canon has a monopoly, the knee jerk reaction would be of course not, there is Nikon/Sony/etc. But 60% market share is getting pretty high. I know a "monopoly" does not have to be 100% market share...but I do not know where the gray zone really starts.
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All this said, I was not trying to say I think Canon is doing this. It is just something that will be interesting to see how it plays out. How hard is it for third party manufacturers to reverse engineer the new protocols? If it becomes next to impossible....I could see a complaint being filed.