To gain the meaning of accursed is beyond "scripture interpreting scripture", for this reason we must look to other sources. Word search "anathema" in Google you will see it is a word with evolved meaning. Even though it can mean "to be destroyed" it also carries the meaning of excommunication.. the two are related.
Compare with:
1 Cor 5:13 God will judge those on the outside; but as the Scriptures say, "You must remove the evil person from among you."
God judges the outsiders.. but God asks us (particularly the elders) to judge those within our congregation. In other words.. God's judgement on believers is executed by us banishing a person from fellowship. And then once they are outside fellowship.. they are open to God's judgement as an outsider.
BORROWED FROM:
Let Him Be Accursed | Learn The Bible
Let's look at the verse in question.
Galatians 1:9
“As we said before, so say I now again, If any man
preach any other gospel unto you than that ye have received, let him be accursed.”
First off I would like to clarify what “that ye have received” means. Please remember that the epistles were literal letters written to literal churches, people etc. Paul or someone he taught delivered the gospel to these churches so he could be confident to say that the gospel they had received was the true gospel. This does not apply directly to everyone today because some have received a gospel, but it is not the same gospel that Paul preached.
Now let us look at the phrase “let him be accursed.” Some of the modern versions will translate this phrase as “condemned to hell”. The problem with this is instead of translating it for you, they have interpreted it for you and have done so incorrectly. The best way to interpret any scripture is by letting the Bible interpret itself. Let’s look at the uses of the different forms of the word “accursed”.
Cursed
- The Serpent (Genesis 3:14)
- The Ground (Genesis 3:17)
- Cain (Genesis 4:11)
- Canaan (Genesis 9:25)
- The Anger of Simeon and Levi (Genesis 49:7)
- The Man that rebuilds Jericho (Joshua 6:26)
- Jezebel (2 Kings 9:34)
Accursed
- He that is hanged on a tree (Deuteronomy 21:23)
- The City of Jericho (Joshua 6:17)
- The Things Consecrated unto the Lord (Joshua 6:18)
- The Children of Israel (Joshua 7:12)
- The Apostle Paul wished of Himself (Romans 9:3)
- No man by the Spirit calls Jesus accursed (1 Corinthians 12:3)
Now that we have seen these occurrences in scripture, let us plug in a couple of definitions for “let him be accursed”. If it means “condemned to hell,” then we must say that the ground in Genesis 3:17, the anger of Simeon and Levi (in Genesis 49:7), anyone hung on tree (Deuteronomy 21:23), the city of Jericho (Joshua 6:17), and the children of Israel (Joshua 7:1) are all condemned to hell.
This does not fit with the rest of scripture.
Another problem with the idea of those preaching another gospel being condemned to hell is that our gospel is very plain that salvation is only by grace through faith and that there are no works involved (Ephesians 2:8-9). There are many who preach that you can only be saved by grace but you must live it in order to keep your salvation. Let’s apply the verse to this person. They got saved “by grace through faith”, yet someone taught them that they could lose their salvation and so they began preaching this to others. This is not the true gospel so according to the interpretation given by most this person would now be condemned to hell for preaching a false gospel but if they can now lose it then they were preaching the right gospel in the first place. This just goes to show that this interpretation does not work.
Deuteronomy 21:23
will give us a key for interpreting the usage and purpose of someone being accursed.
Deuteronomy 21:23
His body shall not remain all night upon the tree, but thou shalt in any wise bury him that day; (for he that is hanged is accursed of God

that thy land be not defiled, which the LORD thy God giveth thee for an inheritance.
The person that was hung on the tree was accursed so that the land would not be defiled. What does this mean? It means that the children of Israel were to put this man out of the congregation (death in the Old Testament) so as to not defile the land for those who were innocent. This applies very well in context with what Paul is saying in Galatians. If you have someone in the church that is preaching a false gospel, then it is very likely that there will be some young believers who will be led astray. So what were they to do? They were to “let him be accursed” or remove him from the congregation so that the rest were not defiled by his false teaching. In the New Testament we are not to kill those who do not preach sound doctrine, but we are to remove them from our church before they corrupt others.
God desires purity in the church and that includes purity in doctrine. The local assemblies are not to be defiled by someone preaching another gospel even if it is a twist on the truth.
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it is also of note that Paul writes later of Jesus in Galatians 3:10-14
10For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them.
11But that no man is justified by the law in the sight of God, it is evident: for, The just shall live by faith.
12And the law is not of faith: but, The man that doeth them shall live in them.
13Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree:
14That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith.