When Paul was writing to the early Christians and telling them not to let anyone judge you by what you eat or drink, a New Moon celebration, or a sabbath day, these were all the things written in the Book of the Law on parchment paper, written by Moses. This book was placed beside the Ark.
Paul wasn’t speaking of the Law of God – the Ten Commandments, which were written by God himself in stone and placed inside the Ark, directly below the Mercy Seat.
Those ceremonial types and shadows were done away with at the cross. There were ceremonial sabbaths that fell on various days of the week. There were even ceremonial sabbath years (Leviticus 25).
Below are some texts to help illustrate the difference:
And it came to pass, when Moses had made an end of writing the words of this law in a book, until they were finished,
Deuteronomy 31:24-26
that Moses commanded the Levites, that bare the ark of the covenant of Jehovah, saying,
Take this book of the law, and put it by the side of the ark of the covenant of Jehovah your God, that it may be there for a witness against thee.
And thou shalt put the mercy-seat above upon the ark; and in the ark thou shalt put the testimony that I shall give thee.
Exodus 25:21, 31:18
And he gave unto Moses, when he had made an end of communing with him upon mount Sinai, the two tables of the testimony, tables of stone, written with the finger of God.