Why is bridge unusual among card games with official rules?

Bridge is unusual among card games because it is one of the few games whose official rules, as promulgated by the World Bridge Federation, are universally followed.1

While most card games are considered folk games—varying by region and lacking a single authoritative set of rules—bridge requires a standardized code to ensure that competitors from different areas can play together in clubs and tournaments without negotiating rules during play. This high level of codification is rare for nonathletic games, with the exception of chess.12

Historically, bridge evolved from whist and underwent several transitions in its governing bodies, moving from local clubs like the Portland Club of London and the Whist Club of New York to international oversight. Today, these universal rules help maintain consistency across duplicate bridge and other competitive formats, distinguishing bridge from games like poker, which often rely on a mix of agreed-upon tournament rules and local, informal variations.21