I find this debate very interesting. I think we all agree that we should interpret scripture from scripture. So lets look at what the Bible says.
1 Corinthians 11:27 So then, whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of sinning against the body and blood of the Lord.
2 Timothy 4: 1-5 In the presence of God and of Christ Jesus, who will judge the living and the dead, and in view of his appearing and his kingdom, I give you this charge: Preach the word; be prepared in season and out of season; correct, rebuke and encouragewith great patience and careful instruction. For the time will come when people will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear. They will turn their ears away from the truth and turn aside to myths. But you, keep your head in all situations, endure hardship, do the work of an evangelist, discharge all the duties of your ministry.
Supporters for closed communion are looking at these verses as justification for the practice. 1 Corinthians clearly says that the Lords Supper should not be taken in an unworthy manner. They then use the role of a pastor, outlined in 1 & 2 Timothy, to be the person that shepherds their congregation and decides what is unworthy. In this case, its anyone that does not believe in their church doctrine or lives in unrepentant sin.
Biblical, that is all I could find to support closed communion.
You obviously didn't look good enough.
Let's look at what else Scripture says:
Acts 2:44 And all those who had believed were together, and had all things in common.
1 Corinthians 10:16 Is not the cup of blessing which we bless a sharing in the blood of Christ? Is not the bread which we break a sharing in the body of Christ?
This speaks to the unity of belief. Do those who deny the real presence of the body and blood of Christ, thus rejecting the clear teaching of Jesus in the Scriptures, truly believe in Jesus and His word? Their very confession says No.
Hebrews 13:17 Obey your leaders, and submit to them; for they keep watch over your souls, as those who will give an account. Let them do this with joy and not with grief, for this would be unprofitable for you.
This speaks to the authority of leaders which includes leaders in the Church and the authority granted them through Christ.
1 Corinthians 4:1 Let a man regard us in this manner, as servants of Christ, and stewards of the mysteries of God.
The Latin "mysterium" speaks of the Sacraments. The servants of Christ in the Church, meaning pastors, are to keep the Sacraments sacred. This includes that their reception is for the edification of the recipients, not to their judgement. Pastors are to be the caretakers of souls. A pastor has the duty to protect the flock that he has been placed over.
Now lets look at what else the bible says.
1 Corinthians (11:28-29), Everyone ought to examine themselves before they eat of the bread and drink from the cup. For those who eat and drink without discerning the body of Christ eat and drink judgment on themselves.
This is speaking to the individual recipient, who is to consider their sinfuless and their personal repentance. Those who are unrepentant should not partake, lest they bring judgement upon themselves. If a pastor, as a steward of the mysteries and the guardian of souls, knows that one is unrepentant, it is his duty to prevent that person from bringing judgement upon himself
1 Corinthians 11:33-34, So then, my brothers and sisters, when you gather to eat, you should all eat together. Anyone who is hungry should eat something at home, so that when you meet together it may not result in judgment.
This is an admonishment against those who were misusing the Lord's Supper. Paul is instructing them on the importance of keeping the sacrament sacred and not turning into a free-for-all or a party.
Matthew 26:14-28 For the sake of space I will paraphrase. Judas agrees to betray Jesus before the Passover meal. Judas then partakes in the Lords Supper, administered by Jesus. Verse 27-28, Then he took a cup, and when he had given thanks, he gave it to them, saying, Drink from it, all of you. This is my blood of the covenant, which is poured out for many for the forgiveness of sins.
John 10: 14-15, I am the good shepherd; I know my sheep and my sheep know me just as the Father knows me and I know the Fatherand I lay down my life for the sheep.
The verses in 1 Corinthians show that it is up to the individual to make good judgment. Corinthians was a letter to the church body, not an individual priest. In Matthew, Jesus did commune Judas even though Jesus knew that Judas had already betrayed him and had not repent. In John, Jesus says that he is the good shepherd. Not the human office of pastor. If Jesus did not deny a person that lived in unrepentant sin, then what human has the authority to deny under the cloak of being a shepherd.
And Judas ate and drank to his judgement. This serves as the perfect example of one who ate and drank unworthily.
As to the office of pastor, it was instituted by Christ and given the authority to take such action.
Matthew 18:18 Truly I say to you, whatever you shall bind on earth shall be bound in heaven; and whatever you loose on earth shall be loosed in heaven.
When the Bible was written there were not all these denominations. To deny communion because you do not agree or know their church membership is not founded in the Bible. All denominations and followers of Christ believe in the Nicene and Apostles Creed. That belief is all that seems to be required by the Bible. Anything beyond that is just church doctrine.
What is required in Scripture is belief in Christ. How can one who rejects His clear teachings, especially regarding the very nature of His Supper, be deemed worthy to receive it? Biblically, they can't.