The European Union (EU) has passed legislation that could be the single biggest threat to Apple’s walled garden.

The EU approved the Digital Markets Act (DMA) in March 2022, legislation that is aimed at so-called “gatekeeper” companies. Gatekeepers are companies that run a “platform,” have at least 45,000 active users, and a market cap of at least $82 billion.

The DMA’s goal is to prevent gatekeeper companies from preferring their own apps or services over those of competitors. In addition, the legislation would ensure users could choose the default apps of their choice.

The DMA went into effect Tuesday and could completely upend how Apple does business. According to MacRumors, the DMA could force Apple to allow third-party app stores, allow users to sideload apps, and even make iMessage compatible with other messaging services.

Although the DMA went into effect Tuesday, there are several implementation steps before companies are required to comply. Once the various steps are taken, companies impacted by the DMA will be required to comply by March 6, 2024, at the latest.

While the legislation promises to address many of the inequities with Big Tech, experts worry that it may cause as many problems as it solves. In particular, the requirement that companies make their messaging apps interoperable with competing services could open a Pandora’s Box of problems.

Because many messaging services use end-to-end encryption (E2EE), exports worry that the DMA will force companies to weaken, or outright break, encryption in an effort to pass messages from one service or another. There is also the possibility that companies may simply decide it is too difficult to maintain cross-platform encryption and abandon it altogether.

There are still many unanswered questions about how the DMA will operate, including whether it will hold up to legal challenges. In our previous coverage, we quoted a Facebook engineer’s statement to The Verge regarding the issues the DMA raises:

“If you went into a McDonald’s and said, ‘In the interest of breaking corporate monopolies, I demand that you include a sushi platter from some other restaurant with my order,’ they would rightly just stare at you,” Alec Muffett, former Facebook engineer and internet security expert, said. “What happens when the requested sushi arrives by courier at McDonald’s from the ostensibly requested sushi restaurant? Can and should McDonald’s serve that sushi to the customer? Was the courier legitimate? Was it prepared safely?”