So as not to make a mockery of the sacred scriptures I will put this odd verse in context for everyone. First, here is a little more surrounding the verse (from the Douay-Rheims, so it reads a little different)
St. Paul here is talking about no longer being "yoked" to the old Mosaic law. Christ came to being a new covenant which is fulfilled in the life of his Church. To those who wish to follow the old law and be circumcised because they feel it is still needed regardless of the new covenant place themselves under the entirety of the law. Why? Because by believing circumcision is necessary they really aren't believing in Jesus' message or his divinity. It is deeper than that and I will allow more learned scholars than I to go into greater detail. I know there are a few out there. ;-)
Galatians 51Stand fast, and be not held again under the yoke of bondage.
2Behold, I Paul tell you, that if you be circumcised, Christ shall profit you nothing.
3And I testify again to every man circumcising himself, that he is a debtor to the whole law.
4You are made void of Christ, you who are justified in the law: you are fallen from grace.
5For we in spirit, by faith, wait for the hope of justice.
6For in Christ Jesus neither circumcision availeth any thing, nor uncircumcision: but faith that worketh by charity.
7You did run well, who hath hindered you, that you should not obey the truth?
8This persuasion is not from him that calleth you.
9A little leaven corrupteth the whole lump.
10I have confidence in you in the Lord: that you will not be of another mind: but he that troubleth you, shall bear the judgment, whosoever he be.
11And I, brethren, if I yet preach circumcision, why do I yet suffer persecution? Then is the scandal of the cross made void.
12I would they were even cut off, who trouble you.
13For you, brethren, have been called unto liberty: only make not liberty an occasion to the flesh, but by charity of the spirit serve one another.
14For all the law is fulfilled in one word: Thou shalt love thy neighbour as thyself.