The effect of the law remaining is to show nobody can keep the law. Even when Israel receives her covenant in the Messianic Kingdom, she will not be under the law but under the Spirit of the law and Christ reigning in Person.

She will try to reinstate her sacrifices in some form or another during the last week consummation then the Antichrist will cut it off and the Great Tribulation commences.

In the millennial kingdom Israel will be a in new dispensation, along with other nations, with the Son of Man reigning in Person on Earth for 1000 years before the new city and the new earth commence.

Still people in the millennium will need to be saved, even people in Israel. They must believe individually to be individually saved. There will be no more Church since the mystery age will have passed. So the law remains in the millennium to show they need salvation since nobody can keep the law.

Hallelujah!