Minor Section 5.5, "HTTP Method Support", of CAMP 1.1 states the following:
"As described in Section 6.1, “Transfer Protocol”, Consumers use HTTP [RFC2616] to interact with CAMP defined resources. To foster interoperability it is necessary to define the HTTP methods supported by
each resource. Note that a requirement on the Provider to support a particular HTTP method on a resource does not ensure that all requests to that resource using that method will succeed; it simply guarantees that the Provider will not fail such requests with a 405 (Method Not Allowed) error.
Providers SHALL support the HTTP GET, PUT, and PATCH methods on all of the resources defined in this section. [RE-53]"
However, there are a number of CAMP-defined resources for which this simply does not make sense; there are resources which are essentially "read-only" in nature. For example, one of the "type_definition" resources. Even if you accept the general notion that a client may want to tag various resources for any number of reasons, it is difficult to imagine why someone would attempt to add a tag to a type_definition resource. These resources exist solely to allow the provider to advertise the resource types supported by the platform.
If we accept the idea that some CAMP resources are "read-only", what should a provider do if a client attempts a PUT or a PATCH method on these resources? 405 is the most honest response to such a request.