Internal emails highlight how an advertising company can use its in-house resources to oppose public policy proposals.

One of the world’s largest advertising firms is crafting a campaign to thwart a California bill intended to enhance people’s control over the data that companies collect on them.

According to emails obtained by POLITICO, the Interpublic Group is coordinating an effort against a bill that would make it easier for people to request that data brokers — firms that collect and sell personal information — delete their dossiers.