The CAA RFC specifies that CAA checks should be made all the way up a domain tree, but in reality the chances of a domain having CAA records the more common TLDs (.com, org, .co.uk etc...) are rather slim.

A simply solution is to implement a simple semicolon split ignore list of TLDS in the CAA validator ("com;org;net;se;co.uk") to allow the CA itself to diverge from the RFC.

Note: this list should be case case insensitive, trim spaces and allow for either with periods (.com) or without (com).