It was already legal for customers to buy ad free products and it was legal for companies to sell them.

In any case, the headline oversells the ruling: it's only about changing the conditions for existing customers.

Amazon can let the old contracts run out and sign up people under a new scheme, that allows them to show ads.

Ending the old contracts and asking people to sign up for new ones risks losing customers who don't particularly care about keeping their subscription but didn't bother to cancel either. Which is why Amazon would prefer to keep the old contracts running and unilaterally change the conditions. Defaults matter.

> Which is why Amazon would prefer to keep the old contracts running and unilaterally change the conditions. Defaults matter.

Yes, and that matters in the short run. In the long run, churn is unavoidable.

Aren’t the majority of these contracts month to month, with a few annual ones sprinkled in?

Exactly. This is a pointless discussion. Just a badly executed legal change. Good that they are reminded that they have to stick to the law, but for consumers practically there is no change.

I think they get auto-renewed, and German law places limits on what you can change.

Prime is usually a yearly contract