UN treaties a driver for hate speech legislation- or are they?

Politicians are fond of saying that their signature on a UN treaty is meaningless because the UN does not write the law in NZ. However it is just these signatures that are being used as part of the justification for Jacinda Ardern’s vile attacks on our freedom to express political opinion.
In their propaganda leaflet (download link below) advocating for the imposition of new “hate speech” laws, the govt refers to two UN treaties in a section entitled “International human rights treaties require legislation against hate speech.” They say-
Inciting hatred is prohibited under international human rights treaties. Aotearoa is party to the International Convention on the Elimination of All Forms of Racial Discrimination (CERD), which requires states to legislate against racist hate speech, which Aotearoa has done. The International Covenant on Civil and Political Rights (ICCPR) also requires laws against advocating national, racial or religious hatred that amounts to inciting others to discrimination, hostility or violence.
You see how it works? When it suits them they say such treaties have no effect, and again when it suits them, they will say the opposite.
As for the UN not making the laws in NZ, that is a deliberate and cynical deflection. Of course the UN does not make the laws. It merely writes the templates for the legislation, which are then adapted for the particular country, and then put into effect by local or national governments.
The National Party ratified CERD on 22nd November 1972 (three days before losing the election). They had previously signed the convention on 25th of October 1966, one month before the election they won.
The National Party also ratified the ICCPR in 1978. However there’s a catch, and it throws Jacinda’s claim that this agreement underpins her new laws into doubt. NZ claimed exemption from the agreement as specified-
The Government of New Zealand having legislated in the areas of the advocacy of national and racial hatred and the exciting of hostility or ill will against any group of persons, and having regard to the right of freedom of speech, reserves the right not to introduce further legislation with regard to article 20.
Article 20 says-
1. Any propaganda for war shall be prohibited by law.
2. Any advocacy of national, racial or religious hatred that constitutes incitement to discrimination, hostility or violence shall be prohibited by law.
So even though NZ ratified the treaty in 1978, it exempted itself from the clause Jacinda Ardern now claims it is bound by. This appears to be just one more untruth from Ardern, whose claim to have never told a lie in politics has been since shattered into a thousand pieces.