What are the rules on the World Bowls stamp and challenging an opponent's bowls?

• Under the laws, the umpire (or marker, if there is no umpire) checks before play that all bowls carry a clearly visible, valid World Bowls Stamp (laws 42.1.2.1 and 43.2.1.1).
• Bowls South Africa domestic regulations:
  • Bowls should have distinguishing marks visible (law 52.1.5).
  • Re-testing and re-stamping are not being enforced until further notice, but only a licensed tester may alter bowls (law 52.2.3). Tampering with the bias can lead to suspension for up to one year (law 52.3.2).
  • Bowls used in the SA Masters should have a World Bowls Stamp no older than 10 years, subject to testing facilities being available (law 53.5).
  • To challenge a set of bowls you must pay a R10 000 cash deposit (law 52.4.4.3). If the bowls pass, the challenger pays the testing costs; if they fail, the owner pays for testing and any re-stamping.

Events can set stricter conditions, for example the 2026 SA Masters required a stamp of the current or a future year and bowls registered before play.