Alternative to properly sourcing is credibility of the author.
When quality newspaper or journalist releases important article with anonymous sources, they rely on their credibility.
It's the same for diplomatic communication. Important sources don't want to end in government papers. They are named only in classified memos. Requiring sources and suspecting employees faking it is not the way to go. If the suspicion arises, people are called back.
That's a good point. But in this particular situation, we know,and the memo says it as well, that lybian were highly divided into rival factions. Some were probably sided with the french gov and others against. In both cases, you can't rely on any of those factions to provide an honest reporting of the true reasons for the french actions.
The only reasoning can be made either from french sources inside the government, that is the people who took the decisions, or by careful fact analysis and deductions. Quoting "knowledgeable sources" without mentionning the reason those sources are knowledgeable is deeply insufficient to base any decision upon, IMHO.
When quality newspaper or journalist releases important article with anonymous sources, they rely on their credibility.
It's the same for diplomatic communication. Important sources don't want to end in government papers. They are named only in classified memos. Requiring sources and suspecting employees faking it is not the way to go. If the suspicion arises, people are called back.