Both wordings are acceptable.
Theoretically, the word "doit" should not appear. It was used in the government's motion because it was probably taken directly from the English version. In proper French, the usual translation would be "L'Office régit, par règlement, [...]", it is an obligation to regulate. There is no discretion involved because it says "régit".
Therefore, the French version of Mr. McGuinty's amendment is correct.