We often minimize the importance of having a סנהדרין that was also known as בית דין הגדול, or the great court. The Rambam wrote that when the בית דין הגדול was in operation, there was no מחלוקת, or controversy in Israel.
If a lower court in one of the cities had a dispute and the judges were unable to come up with a decisive answer, they would contact the high court in Jerusalem. Since this court consisted of the most righteous judges, they would always give a satisfactory answer that settled the argument.
The knowledge that there was true justice in the world, gave the general population great peace of mind.
When the Sanhedrin disbanded in the year 358, מחלוקת became rampant among the Jewish people. Everyone did what was right in their own eyes and there was no peace and harmony.
We see from this how essential it is to have judges and courts that execute true justice.
When we pray in שמונה עשרה, the words, השיבה שופטינו כבראשונה, return our judges as of old, we should say these words with greater Kavanah.