Strictly speaking, it's still legal to use hyogai kanji in a person name if:
- You already have a kanji name that existed before the relevant law took effect. Actually there are still great many young native Japanese people who have hyogai kanji as part of their official family names (take 草彅剛 and 澤穂希 for instance). People who were born in Japan before 1951 may have given names with very rare hyogai kanji, too.
- You are from another country that uses kanji (e.g., China) and have applied to be naturalized as a new Japanese citizen. If you have a hyogai kanji as part of your family name, that kanji can be legally registered. For example 崔 is a relatively common Chinese family name but it's still not in the jinmeiyo/joyo kanji list.
See Also: Use of 旧字体 in Japanese names