Romeo has just gotten married to the woman/girl that he thinks that he is completely and totally in love with. Immediately following this he is in a street brawl with Juliet’s cousin, Tybalt, and kills him which leads to Romeo’s banishment from Verona to Mantua. In Act 3, scene 3, Romeo learns of his banishment from the Friar. Romeo says,
“There is no world without Verona walls,
But purgatory, torture, hell itself.
Hence banished is banish'd from the world,
And world's exile is death. Then ‘banishment’
Is death misterm'd. Calling death ‘banishment,’
Thou cut'st my head off with a golden axe
And smilest upon the stroke that murders me. (A. 3, s. 3, lines 18-24)
Here, Romeo reveals his feelings on his banishment. To him, the banishment would be worse than death because he would be taken from all that he knows and has known his entire life; more importantly he would be taken away from his Juliet and would never be able to see her again. This would be worse than death because he is really alive, and being alive he will be able to think about what he can no longer have. Meanwhile, if he had been killed for his crime, he would not be able to ponder over Juliet because he would be dead and his thoughts could not drive him crazy as they could in his banishment. Romeo reveals this when he says,
“'Tis torture, and not mercy. Heaven is here,
Where Juliet lives; and every cat and dog
And little mouse, every unworthy thing,
Live here in heaven and may look on her;
But Romeo may not …” (A. 3, s. 3, lines 30-34)
Banishment is death because it takes him away from his Love, his Life. The only solution would be in Shakespeare's sequel which he didn't get around to, where they rise from the apparent death of the stupor drug and flee to a banishment of life together. As Jesus may have risen to flee to India, out lovers flee to hidden life abroad. Shakespeare was considering this but chose to end the play as is for sobriety's sake.