Official rules on republishing articles?

I work for a non-profit that wants to republish, in entirety, news articles from a variety of sources. I’m trying to research the legalities but I canfind any official, clear information yet. Does anyone here know? Is it really just dependent on the news source?

Non profit has nothing to do with plagiarism which is what re-publishing without permission is. Check the US Government Copyright page for the rules.