Romeo is young and not partial to following the social customs of the day. When he sees a woman that he wants, he goes after her rather than speaking with her father first for permission to court. He's by no means ready to get married at 14 years-old, but justifies himself in the name of love and because he loves family's enemy. Paris, on the other hand, follows the custom of going to the father first to ask permission to date Juliet.
Romeo is also self-absorbed. When Romeo is first presented to the audience, he is in a self-pitying mood about some one he can't have. His juvenile antics continue as he kisses Juliet twice without her permission at the party; he doesn't even present himself to Juliet respectfully because he doesn't tell her his name. He doesn't even ask her what her name is and has to find out by asking the Nurse. It is arguable that Romeo is no respector of rules or others because of his selfish acts.