Relationship and mutual obligations between the artist and gallery owners

[Konstantin]

Yes, and ascribe artists as peasants and estates in the 21 st Century - Do you approve?

That same treaty process, but not violent.
If the artist already venerable and called-(as our Paul for example) and it is all, then yes lock on to any gallery not needed.
And if he can not sell, then come to an agreement with a gallery of some conditions. But conditions may be different, and more importantly are not conditions, but that the result was - the sale.