I think the wording was imprecise vis-a-vis "amendments."
There are the original laws of the Torah, which can never be violated. If the Torah says "thou shalt not", that means "thou shalt not", no matter what! Later laws can be added in the form of new prohibitions or obligations, but they have lesser standing than the original laws of the Torah.
For instance, the Torah clearly allowed a man to have more than one wife. Then a thousand years ago, the rabbis of Europe enacted a takana to ban polygamy.
This ban, however, is of lesser force than a Torah law. For example: if a man and his sister march down the aisle and go through a Jewish wedding ceremony, they are 100% not married because the Torah spells out that brother-sister relationships are incestual. If, however, a married man goes through a marriage ceremony with a single woman who isn't his wife, he has violated the takana of a thousand years ago, but they are now technically married vis-a-vis Jewish law, and she can't marry anyone else unless she undergoes a religious divorce ceremony.