The Supreme Court was constructed by the Quintessons during the Age of Wrath. Befitting the morality of the aliens who constructed it, the Supreme Court was a "court" in only the loosest sense of the word.
The Supreme Court was more like a vicious circus than anything else. Anyone could accuse anyone of anything, and the Quintessons would arrange a kangaroo court to arraign the perpetrator. More often than not, these victims were found "innocent" of their crimes, and imprisoned for life or thrown to Sharkticons. Quintesson justice left the vast majority of Cybertronians too frightened to speak out against their oppressors.