That said, allow us to speak out of character:
Thank you for all the input, folks. After reading all the comments you've convinced us that your solution is the way to go. As such: yes, during the Battle of the Gods, the allied forces did summon various powerful combatants, but one of Pain's powers dispelled them as they arrived on the field, aside from Ma and Pa for whom we have an explanation but HDK what it is. As such, Akatsuki will not be able to use the same method to prevent summons from being used against them again...at least, not until they successfully retrieve Pain.
As an aside: we try to walk a fine line between not disclosing OOC information or opposition capabilities, while still communicating clearly and setting accurate expectations, hence why this post starts with an in-character and follows with an out-of-character statement. That said, it's a safe bet that when word of the Zoo Rush became public knowledge, Akatsuki were highly alarmed and greatly regretted their lack of summon-prevention.
As promised in earlier discussion, you have a 50 XP bounty to spend.
Thank you for being receptive; this is how I personally expected things to shake out and I'm hoping that folks who felt more pessimistic are reassured and update somewhat.
I will be explicitly clear that my reading of what you're saying is that the Akatsuki are unlikely to have this capability, period - when we tested the idea with runes it was not feasible and the Akatsuki do not have an experienced sealmaster who is also a Summoner, which seemingly implies that they lack the capability to develop a paper sealing array which replicates one of the abilities of the Rinnegan. While I initially commented that the Akatsuki having developed this capability between the Zoo Rush and now wouldn't bruise my suspension of disbelief, I'd forgotten that we'd tried and been told it would be effectively impossible. (IIRC, I don't have the citation to hand. Someone else?)
I guess all of that is to say: until the last sentence of the last paragraph, I felt that communication had been clear and that expectations had been set! But reading "Akatsuki were highly alarmed and greatly regretted their lack of summon-prevention" leaves me with a great deal of uncertainty. Some of that is to be expected, but it feels (emphasis on the choice of word; feelings run at right angles to reason, I am not suggesting any degree of intention on your part) like a bit of a rug-pull to have that come so quickly after reassurance of our shared goals of clear communication. A clear answer not immediately followed by something that muddies the waters would be hugely appreciated, if possible.
e: I'm realizing that starting with 'hey thank you this is great!' and ending with 'I'm very uncertain pls halp' while saying that I feel like the rug's been pulled out from under me a bit is, ah, not great form. Let me be clear: I personally am relatively confident that the sentence in question this was an off-the-cuff comment for completeness. If not for the surrounding context/events, my level of uncertainty would not be high enough for me to have made the comments that I made. In this specific instance, it would be
really cool to get a clear QM statement to the tune of 'based on the design work he did with runes Hazo would be [shocked/unsurprised] to find the Akatsuki had developed a paper seal array preventing Summoning given that they don't have a Summoner sealmaster' to definitively set expectations.
On an unrelated note, in future, might you consider throwing problems like this to the playerbase before announcing tentative rulings? A post asking for help ('we realized that Summons should have been at the BotG but can't make that change now; can you generate a bunch of plausible and minimally-disruptive explanations for us? we're asking you to explore the solution space, not vote something in') would have potentially slowed down proceedings somewhat but would have been good for the esprit de corps as well as (credibly) making your lives easier. (In this specific case I think 'Pain did it; here's a quasi-canon citation that it's one of his abilities' would have bubbled up quite quickly resulting in the same time to resolution.) I cheerfully acknowledge that this is highly similar in terms of objective function to what you did, but 'we need your help' hits very differently from 'we have bad news (although we're open to being convinced otherwise)'. If you've already considered and rejected this, please ignore me and be about your business, but it seems like it might be a useful tool in the toolbox going forward.