Yet it's not that simple, as the article shows. First of all, a contract doesn't need to be in writing. Any time you buy a pack of gum, you enter into a contra

Yet it's not that simple, as the article shows. First of all, a contract doesn't need to be in writing. Any time you buy a pack of gum, you enter into a contract–no signatures necessary. If any conflicts arise from a contract, courts have to find a way to elucidate the respective rights and obligations. A naive view of property rights usually doesn't help. In this case, it's not entirely clear who owns what. If I let you put a statue on my front lawn, does that mean I now own the statue? If not: why should a mural be different? It's entirely possible that the wall is one person's property, yet the art remained with the artists–even though the two cannot be physically separated. If you insist on a materialistic view where the artists gave up all rights to the property owner's benefit, I'd argue that the art was possibly worth more than the building, and there's an argument to be made that if you consider the rights as inseparable as their physical embodiments, it should be the artists now owning the building, not the other way around.