If your iOS app is sending location data to third parties, you better make sure you're playing by Apple's rules and getting users' explicit consent. If not, Cupertino may say sayonara to your app.

As was first reported by 9to5Mac, Apple seems to be more strictly enforcing existing App Store rules around app data collection, storage, use, and sharing ahead of General Data Protection Regulation (GDPR) implementation, which takes effect on May 25. As part of the crackdown, the company has been giving the boot to apps that violate sections 5.1.1 and 5.1.2 of its App Store Review Guidelines.

Apple finally decided to start enforcing guidelines on selling location data

via @jeromep1970 pic.twitter.com/YKAWfMBq35 — Thomasbcn (@Thomasbcn) May 7, 2018

"Upon re-evaluation, we found that your app is not in compliance," the company wrote in an email to an affected developer, according to a post on Twitter. "The app transits user location data to third parties without explicit consent from the user and for unapproved purposes."

Apple is advising affected developers to remove any violating "code, frameworks, or SDKs" and resubmit the app for review. "Once a compliant version has been submitted and approved, your app will be returned for sale on the App Store," Apple wrote.

Section 5.1.2 states that developers "may not use or transmit someone's personal data without first obtaining their permission and providing access to information about how and where the data will be used." It goes on to say that "data collected from apps may not be used or shared with third parties for purposes unrelated to improving the user experience or software/hardware performance connected to the app's functionality, or to serve advertising in compliance with the Apple Developer Program License Agreement."