In his comprehensive article on tax treaties and tax avoidance (in the June 2004 issue of the Bulletin), Brian Arnold discussed, among many things, how the OECD Commentaries deal with domestic anti-avoidance rules as rules of fact, not of law. This comment elaborates on the assumption in the Commentaries that anti-avoidance rules are rules of fact and Brian Arnold's assumption that most countries take a factual approach, while some countries take an interpretative approach. The comment also considers the (possible) implications of the choice of approach.