In our view, the expression refers to oral discourse. If the bill spoke of translation, that would be different. Interpretation refers to oral communications, therefore to what is submitted orally to a justice.
The three criteria of linguistic ability that are used for public service employees are reading, understanding and verbal interaction. Generally speaking, candidates have much greater difficulty with verbal interaction. Justices are not required to exhibit verbal interaction skills. Justices are not expected to be able to ask questions in the other language, but they must be able to understand the verbal submission.
In general, I have met many public servants who have told me that they had no problem reading or understanding, but they found it far more difficult to express themselves or write.
We would not expect that justices draft their decisions in both languages. Justices have the right to render their decisions in the language of their choice; that is currently the case.
The requirement to be able to understand the arguments in the language chosen by those submitting them to the court is in fact quite simple.