The debate rages in many nations with respect to just how "open" borders ought to be, and who should be admitted. God's got a very different approach with respect to the Kingdom of Heaven.
The "Immigration Law" for the Kingdom of Heaven was spoken by King Jesus, and it states, "ALL THE FATHER GIVES ME WILL COME TO ME, AND WHOEVER COMES TO ME I WILL NEVER CAST OUT."
For those who desire it, entry is fairly easy. All the fees necessary have been pre-paid. No earthly nation takes that approach.
Here's an interesting twist that no other kingdom takes. The citizenship application for the Kingdom of Heaven is approved automatically for everyone who meets the criteria. If you confess with your mouth that "Jesus is Lord" and believe in your heart that God raised Him from the dead, you immediately establish your eligibility. Your legal profession of citizenship, as well as your renunciation of all allegiance and fidelity to the foreign prince of evil, is accomplished through baptism.
Oh, and it gets better. WAY BETTER!
Once you have been received into the Kingdom, you are adopted and named a co-heir with Christ. He remains, of course, the absolute monarch. We who are allowed entry to His Kingdom and granted citizenship do not possess the right to change His laws. That is because our status as heir is granted, not as a function of our new citizenship, but actually as a function of being adopted by the Sovereign. God has adopted us as His children, and so we receive the rights to share in His inheritance.
As His children, we have “an inheritance that can never perish, spoil or fade," according to the Apostle Peter. This is truly amazing. Former slaves now adopted and received as co-heirs. We are accepted in the beloved, because we who were far away have been brought near by the blood of Christ.
Citizens gather together regularly to celebrate this gift of freedom, citizenship and adoption, and to remind themselves of Who it was that made the gift possible. (And at what price.) That feast is called by many names. The Lord's Supper, Holy Communion, the Mass. By whatever name, when observed according to His instruction, the celebration and remembrance are the same. His life for ours. His blood to pay our price. Accepted and welcomed because of His grace.
And, finally, welcome to remain forever if we so choose. No one can take us away against our will.
HIS BORDERS are open to all who will accept His Son, His law and His Spirit.