2. The decisions of the Boards of Appeal shall be taken by three members, at least two of whom are legally qualified. In certain specific cases, decisions shall be taken by the Grand Board chaired by the President of the Boards of Appeal or by a single member, who shall be legally qualified.
3. In order to determine the special cases which fall under the jurisdiction of the Grand Board, account should be taken of the legal difficulty or the importance of the case or of special circumstances which justify it. Such cases may be referred to the Grand Board:
(a) by the authority of the Boards of Appeal referred to in Article 166(4)(a); or
(b) by the Board handling the case.
4. The Grand Board shall also be responsible for giving reasoned opinions on questions of law referred to it by the Executive Director pursuant to Article 157(4)(l).
5. To determine which specific cases fall under the authority of a single member, account should be taken of the lack of difficulty of the legal or factual matters raised, the limited importance of the individual case or the absence of other specific circumstances. The decision to confer a case on one member in the cases referred to shall be adopted by the Board handling the case.