I have seen this provision in CC&Rs before, and I have seen it enforced by an HOA before. But I've never seen anyone call the police and stop the process. The question is going to be whether, by accepting and agreeing to the CC&Rs, the homeowner waived his right to assert a claim of trespass against the HOA for coming onto his property to make the repairs. Without doing research, I cannot answer that question for sure, but it is definitely an interesting one. I understand that "I don't know" isn't a very satisfactory answer, but in cases like these, often no one knows for sure until a judge has ruled on the issue. I will say, however, that as an HOA, it is a very good idea to have an attorney retained for just these type of issues that arise. I strongly suggest that as an HOA, you contact an attorney who has experience in these matters and have him/her help you not only with this issue, but also with future issues that arise (and they will, believe me they will).
*This answer is intended for informational purposes only and does not establish an attorney-client relationship or give rise to any privilege.
Generally, courts will enforce these types of covenants assuming they were properly created. The HOA does not need a "warrant" but will need a court order allowing enforcement of the covenant and allowing the action of even directing the Sheriff to stand by and enforce the peace. Most likely, the HOA's costs of enforcement will be chargable as a HOA lien on the property.
The HOA should be very careful witht his covenant, as even if it is enforceable without a court order, the HOA could end up liabile to the owner. The result will also fdepend on what it is that the HOA wants to do. It would be good to establish a procedure if the HOA intends to exercise this right often. As a rule it would be a good idea to have a bid or contract in place if work is to be done. It would be good then to get the court to approve the bid or contraqct and authorize that the work be done and that the owner be liable fot the cost. As a general rule it is better to go to court before and event like this than afterwards.