“I own a home in an Arizona subdivision with an HOA. Recently, the HOA amended the CCRs to redefine the common area to include the sidewalks. However, the subdivision plat clearly shows that the sidewalks are located within sidewalk-and-utility easements on the private lots. The original CCRs gave the HOA no authority to expand the boundaries of the common area. The HOA claims they did this in order to have the right to repair the sidewalks, though no repairs are needed at this time. Can the HOA legally claim ownership of the sidewalk on my property?”

This does sound a little fishy. Rather than trying to guess, I would ask the HOA (or their attorney, since HOA members rarely know the answers to questions like these) what gives them the authority to expand the definition of the common area–effectively taking private property? Is there a provision in the (pre-amendment) CC&Rs? A local law? Some other authority?

Once you know what their position is, you will be in a better position to determine how and whether you want to oppose it.