New client-officer role to be taken on by current SEA CEO Nicolas Menat.
Publicis Groupe was best partner from strategy point of view, despite not being the most compelling on price, chairman and CEO says.
Law joined French holding company in April 2018 after 17 years at Interpublic's R/GA.
Will lead the production house along with co-head Chahna Rupani
$4.4 billion deal will also see Publicis Groupe enter a strategic partnership with Epsilon's current owner Alliance Data.
Elections, ICC World Cup, IPL to drive majority growth
Top news, insights and analysis every weekday
Sign up for Campaign Bulletins