The Torah isn't supposed to be altered in any way (Deuteronomy 4:2). But the Torah isn't a law book. In many cases the Hebrew word "torah" is translated as "law" but it really means "teaching". The laws are mostly there to illustrate how to apply the principles to the situation at that time. For example shellfish were unsafe then but are safe now. The idea that laws can be changed is illustrated in Numbers 27:1-11 where the daughters of Zelophehad overturned one of Moses's laws.
Obviously some laws are meant to be eternal, like the ten commandments. But for most Old Testament laws, we should look for the principle behind that law and then apply that principle to make appropriate laws for our time.