Tales of Tolgard
Lawful, in terms of alignment, is a tendency of a person or creature to act lawfully. Law implies honor, obedience, trustworthiness, and reliability. Further, law also includes close mindedness, reactionary adherence to tradition, judgmentally, and a disinclination to adapt to new situations. Lawful sentient beings would argue that laws are the only basis upon which a civilization and society can survive and thrive on.
Law is one extreme on the lawful/chaotic axis.