Google wants regulators to crack open iMessage and force Apple to make the platform work with competing standards, such as RCS.

Google has been very vocal in its criticism of Apple’s walled garden approach to messaging. Apple has considered making iMessage available for Android in the past, but decided against it out of fear it would lead to losing customers.

In recent years, the green vs blue bubble debate has become more intense, with Google putting pressure on Apple to adopt RCS for iPhone to Android communication. Currently, Apple devices fall back to SMS for non-iPhone communication, leaving users without the security or advanced features iMessage provides. By falling back to RCS instead of SMS, iPhone to Android communication would still maintain the same feature parity as iPhone to iPhone conversations.

Because Apple has rebuffed all calls to adopt RCS, Google is now appealing to the EU to regulate iMessage under the new Digital Markets Act, according to The Verge.

“Through iMessage, business users are only able to send enriched messages to iOS users and must rely on traditional SMS for all the other end users,” the letter, which was sent to internal market commissioner Thierry Breton, reportedly reads. iMessage is an important gateway between businesses and their customers, and this is “without doubt justification for Apple’s designation as gatekeeper for its iMessage service,” reads a letter to the EU Commission that was signed by a Google senior vice-president, as well as the CEOs of Deutsche Telekom, Orange, Telefónica, and Vodafone.

If the EU rules iMessage is a “core platform service,” it could require Apple to make iMessage interoperable with competing messaging platforms and technologies, such as Signal, WhatsApp, and RCS.