In 2019 Lufthansa abruptly terminated the ability to transfer points from Marriott, Hyatt, Hilton and others into Miles & More. That made it tough for Americans to get their points. For most, it meant you’d need to spend on a Barclays-issued co-brand Miles & More credit card, or credit flights to Lufthansa’s frequent flyer program.
The explanation at the time was that German law made it impossible for them to continue allowing. Germany’s Payment Services Supervision Act was being interpreted to count a mileage transfer as a payment service which requires registration, government supervision, and “strong customer authentication” among other requirements.