"According to the Torah which they shall teach you..."Deuteronomy 17:11.

We are commanded to obey the High Court (Sanhedrin) and heed all their decisions with regards to what is permitted or prohibited. This is true whether their decision is based on oral tradition, they arrived at their decision via extrapolation from the words of the Torah, or if the rule was issued in order to address a contemporary concern, i.e., the court saw the need to impose a certain law in order to safeguard a Torah law.