question of law

Short definition from Wiktionary

Noun

1. 1
   An issue to be decided by the judge, concerning the application or interpretation of the law.
2. 2
   A question that the law itself has authoritatively answered, so that the court may not answer it as a matter of discretion.
3. 3
   An issue about what the law is on a particular point; an issue in which the parties argue about, and the court must decide, what the true rule of law is.
4. 4
   An issue that, although it may turn on a factual point, is reserved for the court and excluded from the jury; an issue that is exclusively within the province of the judge and not the jury.