Back in November 2010, Google News launched a new set of tags to let publishers say if they are syndicating other's content. In a sense, Google was asking publishers to admit and tell the truth if they didn't break a story and tell Google which competing publication did break the story.
Basically, Google wanted content writers to tell the truth.
I guess it didn't work out because on Friday, Google deprecated the syndication tag.
Erik from Google wrote in a Google News Help thread:
We wanted to let you know about some new content in our Help Center regarding how to best address the issue of duplicate content across multiple news sites or properties. In short, the
tag has been deprecated, and the remaining options are more consistent with the existing guidance in this area for Google Web Search.
If you have any questions, please feel free to post them in this thread.
So yea, now, you should either use the canonical tag or block Googlebot from accessing the content.
Forum discussion at Google News Help.
Image credit to ShutterStock for truth telling image