Gleaning is honorable work, a grace provision of the Lord for poor people. Where the Lord provides prosperity in a community, there is enough in the leftovers to care for the indigent. The principle is that prosperity comes to an individual so that provision might be made for those who are in genuine need of help. Both the rich and the poor trust God for the provision He makes for them. The situation is that all the farmers work in one large field.
Ownership is vested in parts of the one big field.
Ruth will try to find a sympathetic farmer to glean with. While the law applied to everyone, a hostile or greedy landowner could break the law or find ways to make life miserable for the gleaners. And Ruth was undoubtedly aware that she could run into some prejudice because of her nationality. There are always plenty of reasons a person can find for hoarding his goods to himself. The history of the Jews has plenty of examples of how people developed ways to get around the laws of God.