Actually, HOAs can and do add, change or modify rules irrespective of any CC&Rs, the most recent example in my HOA being a modification which allows CERT member hams to have antennas of a prescribed type, size and location where the CC&R states no antennas.
HOAs definitely can and do write rules as well as grant modification and waivers from those rules. Such misunderstandings seem to be prevalent on this forum.
Apparently, this is not a blanket statement that applies to all HOA's/CC&R's. In my community's Declaration of CC&R's, its provisions can only be amended (I assume "amended" means changed, modified, added, or deleted) by a 90% approval vote of its resident members in the first 20 years from the date of Declaration, and a 75% approval vote after 20 years. In all practically, in a community of 1,000+ homes, this is virtually an impossibility. In my 17+ years of living here, I've never received a notice of a proposed CC&R amendment for a vote. To me, this means that the HOA board by itself cannot "amend" the CC&R's per se. Dissolution of the HOA, and thereby enforcement of the CC&R's, also needs a 90% approval vote by the resident members. But *I believe* the CC&R's would still be in effect, and a neighbor can sue you for a violation.
Now, if the HOA Board has a Design Review/Architectural Committee, they can grant a project request approval/denial to a resident on an individual basis within the general guidelines of the CC&R's. In a previous community I lived in with antenna restrictions, I was given approval for a multi-band vertical, with the stipulation that if a neighbor complained, I would then have to remove it. So the CC&R was still in effect, pending neighbors' approval (which I obtained beforehand). Seems counter-intuitive, but I rode with it.
Let me also say that I'm not an attorney...there's tons of mumbo-jumbo "legalize" in the Declaration...so my interpretations above might be off base

. If anyone can correct me, I'm all ears. I'm just saying that not all Declarations of CC&R's across the Country have the same stipulations written in them. Read yours carefully, and seek legal advice upon any confusion.
73, Bob K7JQ