Can a player leave the green, and when is a substitute allowed?

Under law 32:

• No player may delay play by leaving the rink of play or their team unless their opponent agrees, and then only for no more than 10 minutes.
• In a team or side game, if a player must leave the green through illness or another reasonable cause and cannot return within 10 minutes, the umpire or Controlling Body can approve a substitute.
• A substitute is introduced only if both skips (or, if they cannot agree, the umpire or Controlling Body) think it is necessary.
• The substitute must play in any position other than skip, and the rest of the team can rearrange their positions as necessary.
• The Controlling Body decides the substitute's eligibility. If no eligible substitute is available in a team game, the team forfeits the game.
• In Singles, a player who must leave and cannot return within 10 minutes forfeits the game.
• A player or team that breaks law 32 forfeits the game.
• Member National Authorities can decide the requirements for introducing a substitute in domestic play (law 32.9).

Source: World Bowls, Laws of the Sport of Bowls Crystal Mark Fourth Edition, law 32, https://www.worldbowls.com/wp-content/uploads/2023/05/Laws_of_the_Sport_Fourth_Edition.pdf