Thanks for the extra info. It’s interesting that have one case where it appears the required representation at the meeting is defined but not the required voting majority (the clause in the OP), and three cases where the required voting majority is defined but not the required representation at the meeting ("… must be approved … by the affirmative vote of … 67% or more of the votes cast by the Members present a a duly-called meeting …", “… the affirmative vote of majority of the votes cast by the Members present …” and “… any such rule or regulation adopted by the Board may be amended or repealed by the affirmative vote of a majority of the votes cast by the Members present”).
The language is fairly consistent in the three cases where the majority required for a motion to be passed is defined, which strengthens the case that the different language used in the clause in the OP refers instead to the definition of a quorum requirement. However given that each other case explicitly states the majority required, its absence in the one clause is odd. I could see an argument that the 2/3rds requirement was meant to apply to both the attendance at the meeting and the voting majority, but I still maintain that the actual wording does not support that argument.
The next thing I would consider is whether some sort of equivalency between clauses can be found. Given that we know what vote is required in some instances, which one of those (if any) is most similar to amending the Declaration? I should state here that I didn’t know what a “Declaration” was until a few minutes ago when I took to Google, so from here on in I may be making assumptions which are not valid.
The three cases we have are:
[li]Taking a given property out of the original Declaration[/li][li]Appointing auditors[/li][li]Changing the association’s governing rules (by-laws)[/li][/ol]
We can disregard the second point - it makes sense that the bar for appointing auditors is fairly low.
Number 1. is a drastic move (at least it seems that way to me), so a 2/3 majority makes sense. For number 3. I can see arguments both ways, but here the decision was made to go with a simple majority.
Now the question is whether amending the Declaration more closely resembles taking a property out of the Declaration or changing the rules by which the association is governed.
[Actually, I’ve just had a thought which makes kind of makes any other considerations moot. Given that only a simple majority is required to change the rules, before the vote on amending the Declaration is taken the meeting could always vote to add a rule explicitly stating that only a simple majority is required to amend the Declaration, then job done. ]
My instinct would be that amending the Declaration and amending the by-laws are analogous given that they both involve “changing the rules” and so a simple majority applies.
I would also be putting a motion to the next meeting to amend the by-laws to clarify that position.