Performs dynamic validation of signed code.
Validates a static code object.
This function obtains and verifies the signature on the code specified by the code object. It checks the validity of all sealed components, including resources (if any). It validates the code against a code requirement if one is specified. The call succeeds if all these conditions are satisfactory. This call is only secure if the code is not subject to concurrent modification, and the outcome is only valid as long as the code remains unmodified. If the underlying file system has dynamic characteristics, such as a network file system, union mount, or FUSE, you must consider how secure the code is from modification after validation.
So given this description for codesigning document from Apple, it is not clear what do they mean "dynamic characaterstics" here.