Love, alone, because, as It were, it has a built-in moral compass, enabling it to 'home' intuitively upon the deepest need of the other, can allow itself to be directed completely by the situation. Joseph Fletcher says there are three approaches in making moral decisions, namely, the legal, the antinomian, and the situational approach. Legalism enters every situation encumbered with prefabricated rules and regulations. The letter of the law reigns. Principles, codified in rules are directives, not merely guidelines.
Solutions are preset.
You can look them up in a book. It may develop into a systematic drawing out of rules as to when rules may be broken. Antinomianism is the very opposite of legalism. Literally, it means against law and may issue in licence. One enters into the decision making situation armed with no principles or maxims whatsoever, to say nothing of rules.