As cloud computing becomes increasingly central to enterprise IT, a deepening dispute over software licensing practices is raising serious questions about fair competition. In its latest submission to the UK’s Competition and Markets Authority (CMA), AWS claims Microsoft is using restrictive and costly licensing terms to stifle competition in the cloud market.

Microsoft’s tight integration deters customers from shifting Azure workloads to AWS, even though AWS estimates that up to half of those workloads would move to its infrastructure if the cost of running Microsoft software elsewhere weren’t so high.

The CMA’s ongoing cloud services market investigation appears to support parts of AWS’s complaint. The regulator notes that Microsoft’s licensing model, altered in 2019, has made it up to four times more expensive to run Windows Server on rival platforms.

While Microsoft insists these rules are necessary to protect its intellectual property, AWS and Google argue the pricing structure effectively locks customers into Azure. These restrictions, they say, force customers to repurchase software they already own if they want to run it on another cloud provider—raising their overall costs and limiting genuine choice.

Google echoed AWS’s concerns, pointing to a customer that favored Google Cloud’s capabilities but moved to Azure solely due to licensing economics. Both companies claim that Microsoft deliberately designs its practices not only to compete but also to prevent customers from migrating.

Microsoft, for its part, pushed back, stating that competitors still have sufficient margin to attract customers, and that its licensing strategy supports broader ecosystem value.

The CMA plans to release its final decision in July. With billions of pounds in cloud infrastructure spending at stake—and a global market watching closely—the ruling could mark a pivotal moment in how governments address cloud competition and software portability.