Pre-WAR Legacy uses all the normal rules for playing ordinary Legacy. This explicitly includes using the current "London" mulligan rule. The only difference is the use of a different banned and restricted list; differences will be in boldface font for emphasis.
The following cards are banned:
Cards with a name originally printed in the War of the Spark expansion, or any set released at a later date (May 3, 2019).
25 cards with the Card Type “Conspiracy.”
9 cards that reference "playing for ante."
Bazaar of Baghdad
Dig Through Time
Library of Alexandria
Oath of Druids
Sensei's Divining Top
Survival of the Fittest
Wheel of Fortune
For ease of reference, the ten most recent sets that added cards to the format (i.e.: Legacy-legal sets preceding War of the Spark and having original printings) are as follows:
Ravinca Allegiance (RNA)
Game Night (GNT)
Guilds of Ravinca (GRN)
Core Set 2019 (M19)
Global Series: Jiang Yanggu & Mu Yanling (GS1)
Rivals of Ixalan (RIX)