The rules of chess may not be physically enforced, but the are enforced. If someone breaks the rules they are deemed to be cheating, and thereby forfeit the game.
Now consider boxing, a pastime close to my own heart. Boxing was originally a fighting art, which spawned a sport. The sport encompasses rules that have evolved over time. When the sport of boxing is contested in an officially sanctioned bout, those rules are enforced by a referee. When contested outside of that, it is left to the combatants to enforce the rules themselves. An example of one of these rules, is that the fighters are not permitted to kick one another. In addition to the sport having rules, boxing as a whole also has principles. An example of one of these principles is never to cross your legs. There are dozens of principles. These are the things that a trainer imparts, knowledge collectively gleaned from millions of hours of experience. Expertise in these principles is considered essential to success in boxing. These principles are never enforced. When two fighters who are particularly proficient adhere to the principles, connoisseurs of boxing deem the bout to be of exceptionally high quality (even if it wasn’t necessarily entertaining).
Rules, whether in chess or boxing, do not exist to enhance anyone’s chances of winning. Rather they represent a passive (structural) authority that every contestant is required to abide by. In boxing not everyone agrees that the rules are particularly sensible, and many of us would like for there to be less rules, and less stringent enforcement of those rules, as we feel they detract from the game.
Rules are similar to laws, they are intended to be objective, and are less open to interpretation. Their application is rigid. Outside of enforcement not everyone bothers to adhere to them, and they aren’t always strictly enforced, but their purpose is always to exert a form of authority. To passively control or limit someone’s actions, and they have a blanket application remaining in force even under circumstances when there is no obvious rationale for them to apply.
Principles have a strong element of subjectivity. Their adoption is entirely voluntary, and almost always reasonable and sensible. Principles are never enforced. They are guidelines for improving efficiency, for creating optimal outcomes. People are free to adopt and discard principles as they see fit.
Authoritarians often seek to usher in rules masquerading as principles, in the same manner as they seek to usher in rulers masquerading as leaders. Laissez-faire capitalism is structurally authoritarian, in that it prescribes a rigid and objective ruleset to property, whilst leaving the market to be governed by principles. It’s the market that gets to do as it pleases, not the people. The people are constrained by rules. This is very different from anarchism, where the presumption is against structural authority, and what little governance there is, falls to a discrete set of principles.