Motor vehicle guidelines and the definition of "under the influence" are 2 different things. Under the influence, by alcohol or another substance, is determined by how it affects you and is not determined by a numerical value or 1 specific test. It is subjective and yes, a very grey area. Whether out and about or at home, if you are impaired in any way, or think that you are impared...put the guns away. It's not a difficult concept.