I think it's an ambiguous sentence with two possible interpretations: > Only 1 defender, [but any other player] is allowed in the end-gate circle at any time.

I think it's an ambiguous sentence with two possible interpretations: > Only 1 defender, [but any other player] is allowed in the end-gate circle at any time. > Only 1 defender, [and no other player] is allowed in the end-gate circle at any time. I agree that it could use a clarification, but I think as you've noted the first interpretation doesn't make much sense in the game. If I were a referee of this sport, I would certainly interpret the rules as the second sentence. So, if any forward entered the circle at any time, I would penalize them for that. I would use the fact that the rules that that only defenders are allowed in the end-gate, which implies that forwards are not allowed.