Well what do people want?! Is anyone asking?
If people aren't buying French literature from French bookshops without Government subsidy... then maybe people don't want that.
I want to shop locally. I don’t vote for a law to require myself to shop locally. I just go ahead and shop locally.
The only need for a law is to force someone who doesn’t want to shop locally to do so against their will!
I remember reading about an experiment at Google where they reduced snacking by simply putting an opaque cover on the snacks. When people see chocolate bars, there is a chance they'll turn and get one. They may consider they made the decision rationally but they didn't.
In moments of rationality, it seems reasonable to me to devise and legislate ways to protect yourself from future impulses. It's a paradox for sure, but our impulsive/rationale nature is the source of the paradox, and is unavoidable.
When you "ask" the market by offering food, people may rush to the high-calory fastfood offerings. In a moment of reason, you may want to regulate this (e.g. ban fast food ads around kids), so that you don't live in an obese-ridden society.
In the quest for ever increasing safety, someone might ban tap water because one guy choked on it. That would be hilarious.
If everyone thinks like this then the tragedy of the commons occurs. Everyone prefers local businesses to exist over the online monopoly, but nobody changes their purchasing behavior from what is cheap and convenient. By voting restrictions on online monopolies people avert the tragedy of the commons by coordinating (and compelling) what they want.
What’s the commons in this case?
Other people’s bookshops? Other people’s books? They aren’t commons.
