Retreat rule (Law 16) clarification. 

I'm coming to end of my first season a coach for an Under 8's girls team in the Berkshire county girls football league. I'm amazed that there has been continuous confusion around rules, specifically the retreat rule. I’ve spent a lot of time looking closely at the Retreat Line Rule guidance and to me, it's ambiguous. It''s not clear if the rule should be applied on every occasion the keeper has the ball or just after the ball has gone dead. 

The FA wording refers simply to “when the goalkeeper has possession” — it does not limit the rule to dead‑ball situations. There’s no distinction made between possession from open play and possession after the ball has gone out.

If the spirit of the rule is applied then it feels like it should be applied on every occasion.

Please can anyone assist once and for all....and if you can, please provide the supporting FA guidance material.