In Act II of Romeo and Juliet, Friar Laurence oversteps his vows as a priest by interfering with secular matters and marrying Romeo and Juliet. However, this well-meaning act ends up being pivotal to the tragedy of the two lovers. For, had Friar Laurence counseled with the Capulets and the Montagues and explained how intensely Romeo and Juliet were involved, perhaps there could have been a resolution found.
Certainly, without their having been married by Friar Laurence, Juliet would not have become so desperate to kill herself and the scheme of Friar Laurence to have her seem dead would never have come about, nor would Romeo's impulsive act in the tomb which also effected Juliet's death.
In the word's of a character of Shakespeare's: Oh, what a tangled web we weave when first we practice to deceive. The sin of deception is Friar Laurence's. As a priest and an adult, he should not have been as impulsive as the youths; he should have been forthright and open, going to the feuding families as a mediator.