Jesus Fulfilling the Law - An End to One Era and the Beginning of Another

A comment on the article Why Evangelicalism is Failing a Generation asked another poster a tough question.  I thought I would give a shot at answering it

How does your church (or how do you personally) reconcile the fact that all modern christians choose to ignore most of their god's unwavering laws that appear in Leviticus and Deuteronomy?

The ones about not wearing clothes of two different materials, putting unruly children to death, shunning menstruating women and not allowing them into holy places - these laws are laid down in verses immediately proceeding and following the ones that call homosexuality an abomination.

I cannot for the life of me understand how humans who believe in a law-giving god can cling to some laws (mostly those that conveniently sanction or oppress someone else) while utterly ignoring others.

Much greater theologians than me have wrestled with this subject, but here is how I currently work through that great question.  For this article, I am going to ignore the specific issue at hand and deal with the broader principle of the law.

The role of the law in the life of believers was a debate even in the early church.  The whole letter of Galatians was written to a group of Christians who were still living under the law and trying to force others to do the same.  Paul wrote to explain why they did not need to live under the law.  He said, "For freedom Christ has set us free; stand firm therefore, and do not submit again to a yoke of slavery" Gal 5:1 (ESV).  By this time, Paul was describing the law as a "yoke of slavery."  That is not a kind description.  Then he summed up the law after explaining why circumcision was no longer necessary:  
For you were called to freedom, brothers. Only do not use your freedom as an opportunity for the flesh, but through love serve one another. For the whole law is fulfilled in one word: “You shall love your neighbor as yourself.” Gal 5:13-14 (ESV). 
In Matthew 5:17-20, Jesus claimed that he came not to abolish but to fulfill the law.  The end result is the same - the law no longer applies, but the explanation on why it stopped applying is different.  He did not get rid of it.  Instead, he brought the law to its natural conclusion.  The law was like a seed that would spring to life in a new and better way to live with God (Hebrews 7:22, 8:6).  Paul would later explain that the law was not wasted for it revealed sin and led us up to the point of realizing our need of a Savior.  Jesus then went on to say that people would have to be more faithful than the most faithful legalists of his time in order to enter the Kingdom of Heaven.  Jesus' teaching is that without his grace, which came through his fulfilling of the law, nobody would be able to be right with God.

In Romans 3:19-3:31, Paul wrote that nobody would be made right by the law.  The way to righteousness is by faith.  We are each sinners and have violated the law.  Paul states that the law's purpose was to show us what is sin.  He elaborated that we would realize the futility of trying to be righteous under the law.  For once we break one small part of the law, we have broken the whole law (James 2:10).  The law should leave us realizing our great need of grace. 

The writer of Hebrews 7:11-28 talks about when the priesthood is changed, there is a new law.  With Jesus, we moved out of a priesthood of the line of Aaron into the priesthood of Jesus, so we moved out of the Levitical Law into the law of Jesus.  The writer calls this new era a "better covenant."  No longer is there a need for ritual sacrifice because Jesus was the sacrifice for all, and the law has been simplified. 

Jesus narrowed the law down to just one teaching.  He described it as a "new commandment" when it was not new.  One would need to assume that Jesus was not just ignorant or forgetful but that he knew that his "new commandment" was an ancient teaching from Leviticus 19:8.  So what was he saying when he said it is a new commandment when it was an old one?  It would be an inference to the ten commandments and the entire law being fulfilled and the establishment of a new law.  No longer do we need to adhere to the old commands, which allowed people to be legalists and parse the law in such ways that they could follow the letter of the law while ignoring the spirit of the law.  Jesus' new commandment sums up the spirit of the law and in a way that both narrows and broadens it.
A new commandment I give to you, that you love one another: just as I have loved you, you also are to love one another. By this all people will know that you are my disciples, if you have love for one another.  John 13:34-35 (ESV)

And now I ask you, dear lady— not as though I were writing you a new commandment, but the one we have had from the beginning— that we love one another.  And this is love, that we walk according to his commandments; this is the commandment, just as you have heard from the beginning, so that you should walk in it. 2 John 1:5-6 (ESV)