Can our California HOA enforce parking our van in the garage or covering it?

Do not ignore the HOA. It has the power to impose fines and to go to court to either collect the fines or to enforce the HOA's CC&Rs and rules. If it wins, the HOA is entitled to reimbursement for all of its legal fees. These legal fees can get very expensive very fast. Until you work this out, I would recommend complying, so that you don't incur monetary fines or potential liability for the HOA's legal fees.  You need to have a lawyer familiar with HOAs and CC&Rs review your CC&Rs, any rules and any other governing documents. Provided that they do not violate the CC&Rs, the law grants HOA Boards of Directors very very broad discretion to make decisions. On the other hand, there might be language in the governing documents which would not allow the Board to discriminate between cars, pick-up trucks, and vans parked in driveways on the owner's private property. A lawyer familiar with CC&Rs and the state laws regarding CC&Rs would need to review your governing documents very carefully. The HOA Board must also treat everyone the same.  Your best protection against an unreasonably intrusive Board is to elect reasonable Board members. Too many HOA members don't want to spend the time and energy to be involved with their HOA. The result is that many Board members select themselves, because they are the only ones who volunteer. Too often, they volunteer, because they have an agenda which will interfere with other people. The only protection against them is for good people to volunteer and vote out the bad members. Dana Sack