Unfortunately this is a nightmare to regulate. Whatever regulation a government will come up with, amazon (and all other big tech) will do everything to maliciously comply.

Look at the french regulation on book prices. The french "directorate for competition, consumers, fraud punishment" told amazon that they could not sell books with free shipping. Books have regulated price in France to garantee equal access to everyone everywhere. The DGCCRF claimed that offering free shipping de facto lowered the price of the books and was unfair to small local book shops. The next day, amazon introduced €0.01 shipping for books...

I'm all for regulating these assholes to ensure fair competition. But regulating them is not as simple as some people make it sound like. I would hate to be a lawmaker.