What's interesting about sheviit and yovel is that is circumvents not only the palace but also the temple.
The purchase on land tenure does not depend on the cult. That is the deeper meaning of the placement of the two penultimate chapters of Leviticus: they come at the end of the Levitical laws but they are not themselves Levitical.
By tying the laws of sheviit and shemitta to a periodic and predictable sabbatical or jubilee year the Israelite God removes them from the decrees of the ruling class, be it palace- or temple-based.
By that token, it might make sense that the modern day renewal of the laws of sheviit and shemitta ought not to depend on rabbinic participation or approval. It might be that the laws of sabbatical and jubilee are irreducibly populist and must come out of the will of the subjects and not the rulers.