Every language should be whitelisted because a lot of people are adding random languages to their characters because it's easy to. Even in the future, people are not any smarter than they are today, and would need to put effort into learning the languages. Some simple questions would be a good way to determine who does and does not deserve to use a language.
1: Why does your character speak this language?
2: When did they learn this language?
3: How did they learn this language?
4: How does this language affect their life?