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. It finds a guideline in the wisdom of the Church and culture which contains many general rules. But Fletcher hastens to add that in situation ethics the most reverend principles may be thrown aside if they conflict in any concrete case with love. Principles, maxims, are illuminators, not directors.