"He forgave us all our sins, having canceled the written code, with its regulations, that was against us and that stood opposed to us; he took it away, nailing it to the cross." NIV translation
God forgave us of our sins but many times we fail to understand exactly what that means. When we forgive someone, we usually still remember the offense and many times it comes out again in the heat of a disagreement. When God forgives us, He purposely forgets about the offense and it is like it never even happened. Not only did God forgive us but He even "canceled" the law that we were breaking and took it away to where it does not even apply to us anymore. So, if you are in Christ, the Mosaic Law does not apply to you no matter how much people want to try to put you back under that legal system. You are saved by the grace (gift) of God and nothing else!
"And having disarmed the powers and authorities, he made a public spectacle of them, triumphing over them by the cross." NIV translation
Jesus not only nailed the law to the cross but also the power of sin and death. He soundly defeated them with the sacrifice on the cross and with His resurrection in triumph. Because of these facts, we can live the life of victory as they do not have any power over us if we are in Christ.
"Therefore do not let anyone judge you by what you eat or drink, or with regard to a religious festival, a New Moon celebration or a Sabbath day." NIV translation
We are in Christ and the religious laws do not apply to us but many people just can't let go of the law and try to add it to grace. Paul makes it clear that we are not to let anyone try to apply the Law to us in dealing with salvation.
That is the same message that he gave to the Ephesian believers (see Ephesians 2:8 & 9).
"These are a shadow of the things that were to come; the reality, however, is found in Christ." NIV translation
A shadow does not have substance and here Paul explains that the religious laws did not have the ability to bring salvation. The reality is that nobody could be saved by their following of religious routines. That salvation is only available through faith in Jesus Christ as the Son of God. Even today, many get confused with the traditions of a group of believers and forget that our faith is only in Jesus and not what our ancestors may or may not have done.