For a little disclaimer on how these were codified, you can visit the original laws of magic thread.
Laws of Magic
Law of Chaos: Even with proper observance of the Laws, magic is chaotic and dangerous by nature. Spells can go awry. Spell Permanency is a new and specialized field that can only guarantee longevity to within an acceptable margin. The longer a spell goes on the higher the chance it will go awry.
Law of Methods: Methods for manipulation of magic so far include written words and symbols (including glyphs and runic formulas), spoken words and rhymes, color theory, music theory, hand symbols and gestures, esoteric components, and direct energy manipulation. These are all considered means by which a caster can negotiate arcane intent.
Law of Equivalent Exchange: All magic carries comes with a cost. This is usually seen as the consumption of material spell components but can also be seen as physical damage (bruises, cuts, disfigurement, etc), intangibles (sanity, memories, emotions, and in particular secrets), accelerated aging, and in extreme cases even death. Casting magic in a group mitigates this effect.
Law of Arcane Inertia: With rare exception, spells that are cast will remain cast as long as conditions supports their existence. A fireball will burn out with lack of fuel but will not randomly disappear. A curse will remain until its neutralized (or its respective energy source runs out). Contrast against Law of Chaos.
Law of Parallel Symbolism: "Like produces like" or "an effect resembles its cause". It is easier to produce a fire effect from a spell focus related to the base element (coal, a phoenix feather, etc) than an unrelated or neutral component (earth) or diametrically opposed component (water or ice).
Law of Contagion: Objects in contact become entangled and the contact persists over distance but attenuates with time. This law is commonly applied in voodoo, allowing a magician to perform spells on an item and produce an effect on a person or place. Contagion is affected by tangible variables like how many people contacted the item, for how long, and whether the item is part of the target (hair, skin, blood provide a stronger link than clothing). Intangible factors like sentimental attachment and emotional trauma are also a factor. Contagion links can also be semantic or metaphorical.
Law of Rule: Magic is regulated by layers of genius loci (other terms include tutelary deity and daimon), explaining regional differences in arcane practice and efficacy.