掲示板 Forums - About Jōyō Kanji

Newspapers can use non-joyo kanji, though it is customary to include furigana when that happens (or even when using joyo kanji in words that are read in an unconventional way).

It's important to note that what newspapers consider joyo doesn't fully line up with MEXT (the Japanese Ministry of Education). The main goal is to make it easier to read for the general population, so obscure joyo kanji might appear with furigana, but common non-joyo kanji without.

For example, this is the NSK's (Japan Newspaper Publishers and Editors Association) response to the 2010 changes to MEXT's joyo list: https://www.pressnet.or.jp/publication/book/pdf/shimbun_yogo.pdf

You can see that they treat 絆 as joyo, while 朕 is not treated as joyo.

But every newspaper has its own style guide, which can slightly deviate from NSK's.