I understand that in theory everyone can interpret the Torah and find his own Chiddushim from a renown Rabbi to a secular Jew, young and old, Jew and non-Jew. Today we can see myriads of Perushim and whole books by secular Jews and non-Jews with no relation or foundation to our tradition.
Are there any rules that cannot be broken by interpreters that we, the Orthodox Jews will see as legitimate? Or, on the other hand, what interpretation we can clearly say are illegitimate in our view?
For example, can one tell a Chidush that contradicts Rashi, or Gemmorah or the 13 principles?