The General Data Protection Regulation (GDPR) is a regulation in EU law on data protection and privacy for all citizens of the European Union. It states that brands, which are controllers of personal data, need to be able to honor requests for access, portability and erasure within one month.
When it comes to mobile attribution, it is impossible to know which users are European citizens in advance. Therefore, practically GDPR applies on all mobile users, European or not.
To address the new needs arising from GDPR compliancy, AppsFlyer, along with mParticle, Amplitude and Braze, has initiated the OpenGDPR protocol. OpenGDPR enables vendors to easily take data privacy actions across multiple systems that process and store customers' data.
You can read more about the initiative here.