An ordered society protects us from evil.
If you’re lawful good, you respect the authority of personal codes of conduct, laws, and leaders, and you believe that those codes are the best way of achieving your ideals. Just authority promotes the well-being of its subjects and prevents them from harming one another. Lawful good characters believe just as strongly as good ones do in the value of life, and they put even more emphasis on the need for the powerful to protect the weak and lift up the downtrodden. The exemplars of the lawful good alignment are shining champions of what’s right, honorable, and true, risking or even sacrificing their lives to stop the spread of evil in the world.
When leaders exploit their authority for personal gain, when laws grant privileged status to some citizens and reduce others to slavery or untouchable status, law has given in to evil and just authority becomes tyranny. You are not only capable of challenging such injustice, but morally bound to do so. However, you would prefer to work within the system to right such problems rather than resorting to more rebellious and lawless methods.