Should non-believers be allowed in church? Very interesting and very edgy question. The mention of Church in the Bible is often referring to the multitudes of Christians and not just the building. I'm curious about the building in this question.

I know that these days most churches are designed to be seeker-friendly, in a way that their doors are "open" to all individuals during all hours, including service. What I'm curious about, is why some Christians believe that their church should not be opened to the non-believing population during service hours.

More specifically J.H. Skelly and his street preaching ministries believes that non-believers should not be allowed inside of the church during the service hours.

What is the Biblical basis for this kind of thinking?
This is also the case among the Eastern Orthodox - if you're not Orthodox you get as far as the narthex but no further. Their practice is not based solely on scripture, but also on tradition. The basic idea is that the Church is unified as the Body of Christ, and this unity is expressed and sanctified by common participation in the Eucharist; it is therefore wrong to allow people who are not part of the Church to take part in the service. It is a more extreme version than, say, the Catholic position that you can be physically present in the church building, but not go up to receive the sacrament.

Scriptural support for unity through the Eucharist is found principally in 1 Corinthians 10-12 and in John 6:25-59, though there are other passages (like Acts 2:42-47) that speak about unity of the community of believers in a general way. 


  Is not the cup of thanksgiving for which we give thanks a participation in the blood of Christ? And is not the bread that we break a participation in the body of Christ? Because there is one loaf, we, who are many, are one body, for we all share the one loaf.
  (1 Cor 10:16-17, NIV)


The inference is that believers are united, but believers+unbelievers are not, and so there is no true koinonia ("participation" above, also translatable as "fellowship" or "community") if the celebration of the Eucharist does not reflect the unity of Church membership.