What is the play in Duplicate Bridge?

Verdict

After three passes, the defender on presumed declarer's left makes the opening lead face down (Law 41A); Before it is faced, the leader's partner and the presumed declarer may ask for a review of the auction (Law 41B); dummy's hand is then spread; The player who leads to a trick may play any card...

Source: Law 41, Law 44 — American Contract Bridge League — Laws of Duplicate Bridge

Why people argue about this

People often assume that if they face down their lead card before it's asked about in Law 41B, they can play any card from their hand without restriction, which is incorrect. The confusion arises because the rule specifically states that after facing down a trick, the player who led must then follow suit with one of their own cards or the dummy's, not just any card from their hand.

Send this to your friend — argument over.

4. Gameplay (Auction & Play)

The Auction

The auction period begins for a side when either partner withdraws his cards from the board (Law 17A)
The player designated by the board as dealer makes the first call; thereafter each player calls in turn clockwise (Law 17B, 17C)
A bid designates a number of odd tricks — tricks in excess of six — from one to seven, plus a denomination. Pass, double and redouble are calls but not bids (Law 18A)
A bid supersedes a previous bid if it names the same number of odd tricks in a higher-ranking denomination, or a greater number of odd tricks in any denomination (Law 18B)
A bid that supersedes the last bid is sufficient; one that fails to is insufficient (Law 18C, 18D)
Doubles and redoubles increase the scoring stakes of the contract (Law 19)

End of the Auction

The auction ends when, one or more players having bid, there are three consecutive passes — the last bid becomes the contract (Law 22A)
If all four players pass, the hands are returned to the board without play, and there is no redeal (Law 22B)

The Play

After three passes, the defender on presumed declarer's left makes the opening lead face down (Law 41A)
Before it is faced, the leader's partner and the presumed declarer may ask for a review of the auction (Law 41B); dummy's hand is then spread
The player who leads to a trick may play any card in hand; each other player in turn plays a card, and the four cards constitute a trick (Law 44A, 44B)
Each player must follow suit if possible — this obligation takes precedence over all other requirements (Law 44C)
A player unable to follow suit may play any card (Law 44D)
A trick containing a trump is won by the highest trump; a trick without one by the highest card of the suit led (Law 44E, 44F)
The winner of each trick leads to the next (Law 44G)

4. Gameplay (Auction & Play)

The Auction

The auction period begins for a side when either partner withdraws his cards from the board (Law 17A)

The player designated by the board as dealer makes the first call; thereafter each player calls in turn clockwise (Law 17B, 17C)

A bid designates a number of odd tricks — tricks in excess of six — from one to seven, plus a denomination. Pass, double and redouble are calls but not bids (Law 18A)

A bid supersedes a previous bid if it names the same number of odd tricks in a higher-ranking denomination, or a greater number of odd tricks in any denomination (Law 18B)

A bid that supersedes the last bid is sufficient; one that fails to is insufficient (Law 18C, 18D)

Doubles and redoubles increase the scoring stakes of the contract (Law 19)

End of the Auction

The auction ends when, one or more players having bid, there are three consecutive passes — the last bid becomes the contract (Law 22A)

If all four players pass, the hands are returned to the board without play, and there is no redeal (Law 22B)

The Play

After three passes, the defender on presumed declarer's left makes the opening lead face down (Law 41A)

Before it is faced, the leader's partner and the presumed declarer may ask for a review of the auction (Law 41B); dummy's hand is then spread

The player who leads to a trick may play any card in hand; each other player in turn plays a card, and the four cards constitute a trick (Law 44A, 44B)

Each player must follow suit if possible — this obligation takes precedence over all other requirements (Law 44C)

A player unable to follow suit may play any card (Law 44D)

A trick containing a trump is won by the highest trump; a trick without one by the highest card of the suit led (Law 44E, 44F)

The winner of each trick leads to the next (Law 44G)

The Play