It seems fairly clear in the laws that if the throwing team don't have a receiver, that doesn't affect whether the defending team can or can't have one (or vice versa).
Naturally, with two concise & well-defined Definitions ('lineout players' and 'participating players at a lineout'), the law itself (18.14) helpfully refers to 'players in the lineout', which is not actually defined.
It feels natural to me that when talking about numbers, this refers to the total number of participating players.
So having a receiver means that the opponent can choose to have one more player in the line, by not having a receiver.
Right?
Of course the question then arises as to when a team must decide whether they're having a receiver or not.
18.17 says 'once the lineout is formed' there are restrictions on movement - but when exactly is the lineout formed?
Is it when 2 players from each team have formed a line according to 18.9, 18.10 & 18.11?
What about the rest of the lineout players? Or the other participating players?
So many questions...
The throwing team's players may 'change positions with other participating players' before the throw (18.17a) - but this implies that if you start with a receiver, they can't join the line just before the throw - because this is not changing places with another player.
Likewise they can't move from the line to become a receiver at the last moment. And note that the wording of the law entails that moving from the line to receiver is 'leaving the lineout'.
Meanwhile, the defending team may only 'leave the lineout' to adjust numbers (18.17b) - and by comparison with 18.17a, they are therefore prohibited from moving from the line to a receiver position.
So, do teams need to advise whether they're using a receiver or not, at (say) the same time the throwing team nominate the number?
And then 18.18 chimes in that 'participating players may change places in the lineout before the ball is thrown' - presumably 'may change places according to the restrictions in 18.17', but this isn't clear.
What about the non-throwing player within the 5m zone? He's a participating player, but he's expressly not 'in' the line.
I realise I'm overthinking all this - but exploiting details of law is a sport unto itself, and you can drive a coach and horses through these bloody things.
Naturally, with two concise & well-defined Definitions ('lineout players' and 'participating players at a lineout'), the law itself (18.14) helpfully refers to 'players in the lineout', which is not actually defined.
It feels natural to me that when talking about numbers, this refers to the total number of participating players.
So having a receiver means that the opponent can choose to have one more player in the line, by not having a receiver.
Right?
Of course the question then arises as to when a team must decide whether they're having a receiver or not.
18.17 says 'once the lineout is formed' there are restrictions on movement - but when exactly is the lineout formed?
Is it when 2 players from each team have formed a line according to 18.9, 18.10 & 18.11?
What about the rest of the lineout players? Or the other participating players?
So many questions...
The throwing team's players may 'change positions with other participating players' before the throw (18.17a) - but this implies that if you start with a receiver, they can't join the line just before the throw - because this is not changing places with another player.
Likewise they can't move from the line to become a receiver at the last moment. And note that the wording of the law entails that moving from the line to receiver is 'leaving the lineout'.
Meanwhile, the defending team may only 'leave the lineout' to adjust numbers (18.17b) - and by comparison with 18.17a, they are therefore prohibited from moving from the line to a receiver position.
So, do teams need to advise whether they're using a receiver or not, at (say) the same time the throwing team nominate the number?
And then 18.18 chimes in that 'participating players may change places in the lineout before the ball is thrown' - presumably 'may change places according to the restrictions in 18.17', but this isn't clear.
What about the non-throwing player within the 5m zone? He's a participating player, but he's expressly not 'in' the line.
I realise I'm overthinking all this - but exploiting details of law is a sport unto itself, and you can drive a coach and horses through these bloody things.