For example, when a player kicks the ball down field, all of his players in front of him are offside.
Likewise, at a scrum or lineout, the forwards are all offside after the ball has been cleared from the lineout or scrum.
Such players are not usually penalised for being offside because they clearly cannot avoid being in front of the ball being played.
It is only if they attempt to play the ball themselves or interfere that a referee would consider penalising them.
So what is "accidentally offside" and how might a referee deal with this situation?
Accidental offside occurs when an offside player cannot avoid being touched by the ball or a team mate carrying it.
If there is no advantage to the offside player's team when this occurs, play can be allowed to continue.
But if the player's team gains an advantage, then the referee awards a scrum to the opposing team.
The Lions clearly gained an advantage because the ball landed in Owens' arms. And herein lies the nub of the argument.
If the offside player cannot avoid being touched by the ball, a scrum would be the appropriate ruling, assuming the opponents don't gain an advantage by then being able to play the ball themselves.
But two things occurred - Owens clearly caught the ball and the All Blacks seemed to get an advantage because Owens, realising he had played from an offside position, dropped the ball which was then picked up by an All Black, who seemed to have a good chance of scoring a try.
Poite ignored the advantage the All Blacks had gained and focussed on the offside ruling - a lot of things were happening at quick speed in a highly charged last minute of the game and perhaps the official decided he needed to deal with the first offence to avoid confusion - in himself and/or the players.
With the advantage of technology via the Television Match Official (TMO), both Poite and the TMO seemed to agree that Owens was offside and that a penalty should be awarded.
But somewhere between reaching that decision and then speaking to the two captains, Poite seems to have changed his mind and awarded the scrum instead.
Referees generally never change a decision, even if they realise in hindsight that it was wrong.
But decisions can now be changed as a result of a referral to the TMO.
Personally, when I watched it live, my first thought was that the All Blacks would be penalised for captain Kieran Read clumsily clattering into another Lions' player attempting to catch the ball.
That part of the incident seems largely to have been ignored, apart from one British scribe I read in The Times newspaper who was adamant that the Lions should have been awarded the penalty for that offence.
A second scribe in the same paper thought the referee had made the right decision in ruling "accidental" offside.
Nowhere did I read that the All Blacks should have been awarded a penalty for offside play, but then I didn't get to read any local papers.
Andrew Merthens in his column in The Times commented that all French referees are incompetent and cheats.
This was based on his experience playing several seasons in France at a time when the two French referees assigned to the Lions series were "on their way up".
I thought that was a bit harsh.
Whatever your opinion is, the atmosphere in the Irish pub at that time was electric - you'd have thought the Lions had won the match and the series.
We Kiwis simply sat there in stunned silence and contemplated what might, or should, have been.