Nowadays, this authority is not delegated to the current generation's Sages, and thus the Torah can not be commentated on, in matters concerning the Halakha, if it is in contradiction to Chazal's commentary. Earlier on, up until the midst of the Tannaim era, when there was a Sanhedrin (a Jewish law court), Chazal had also the authority to decree predestinations and to enact new religious regulations, in any matter they saw fit, concerning issues that were not included in the written "Torah", or were not handed at Biblical Mount Sinai.
At present, this authority is not passed on to the current generation's Sages, which means that the Torah cannot be interpreted in matters of Halakha if it contradicts Chazal's commentary. In the past, until the time of the Tannaim era and the existence of a Sanhedrin, Chazal had the power to establish predestinations and create new religious regulations as they saw fit regarding issues not covered by the written Torah or not revealed at Mount Sinai.