Shoftim - Rishon
The Supreme Court
Moshe told the Jews to establish a legal system with judges and police in every Tribe. They are responsible to maintain a justice system without corruption. They may not show favoritism or accept bribes, as bribery warps the judgment of even the most honest individual. They must pursue perfect justice and truth so that they can live securely in the land that God has given them.
The Jews are warned against planting asheira trees or erecting pillars for idolatry, since God does not approve. Animals offered for sacrifices must be free of disqualifying defects. If someone is convicted of idolatry, the penalty is stoning, but the death penalty in capital crimes can only be carried out when there are at least two witnesses.
If the local courts are ever stymied in any matter, they can always take it to the "Supreme Court," the Sanhedrin in Jerusalem. This body was not only judicial, it was also legislative. In other words, in addition to deciding court cases, the Sanhedrin was also responsible for interpreting the Torah and passing laws to safeguard it. Not only is the Sanhedrin empowered (and required) to pass Rabbinic laws, verses 10-11 obligate the nation in obeying these laws. (So, "it's only d'rabbanan" doesn't make much sense, since obeying Rabbinic laws IS a Torah law!)
A rebellious elder who openly defies and acts insubordinately to the law commits a capital offense.