William O. Walker who is nearly on the verge of interpolating the Apostle Paul out of existence altogether (Interpolations in the Pauline Letters) concludes his book by saying something like, Just because Paul didn't write 1 Corinthians 13, or Romans 1:17-2:29, or 1 Cor 11:3-16 doesn't mean that it's not authoritative.
Indeed, Walker explicitly says that all of those many passages in the Pauline epistles which he thinks were not penned by Paul are nonetheless canonical and authoritative. Thus, for example, we might surmise that although he believes that Paul didn't write the silenced women passage (1 Cor 14:33-34), he still believes that we should obey the dictates of the spurious passage.
This is a remarkable take, and reflects an extreme view of "canonical criticism" (cf. Brevard Childs' approach to biblical interpretation) and effectively does away with textual criticism. Why bother with textual criticism if you're going to make everything authoritative, even if the original inspired writer didn't write it?
When first embarking on my studies in New Testament, I was naively swayed to take a similar view of canon. For example, I would argue that although John's Gospel did not originally include the story of the woman caught in adultery, it is nonetheless authoritative since it was in our canon of scripture. Way back then, I mentioned this to Gordon Fee once, and he quickly got me straightened out: if the original inspired author didn't write it, it doesn't belong in the canon.
But as I recently hashed out Walker's argument with a text critic, the issue of the Adulterous Woman pericope came back up, with a different twist. Again, most New Testament scholars would deny that this was an original part of John's Gospel. However, many of them would affirm that the story reflects a true historical incident.
Here's my point: If the story is a true historical event (and I think it probably is), then Jesus' teaching in the story is absolutely authoritative, even though it is not canonical. So, we may excise John 8 and the story of the adulterous woman from canon, but assuming its historicity, the irony is that since Jesus did indeed say, "He who is without sin, cast the first stone," we must obey his teaching, even if it is not the inspired word of God!