*nod* what is this in reference to?
If we're talking Golems, it means infinite and unbeatable SR. If a spell or effect doesn't allow SR then it still works.
If we're not talking about Golems, then this would give a good guideline to start from. Generally (there are exceptions, of course) if a spell interacts directly with the creature it allows SR and/or a broad, over-arching "immunity to magic" should apply. Examples: fireball, charm, teleport, healing. If the spell doesn't interact with the creature, but instead makes or does something that the creature has to subsequently deal with, then no immunity should apply. Examples: wall of iron, rock to mud, obscuring mist, summon monster.
Other abilities just use the same model. Spell-like abilities are easy because.. well.. they're spell so they have stat blocks. Supernatural abilities, again the same - if the magic interacts with the target, then its immune (example: a dragon's breath weapon), if the magic doesn't interact with the target, then it functions as normal (example: a creature's regeneration ability). For magic items, if the magic is contained in the item (like a weapon's enhancement bonus), it should still work. If the magic has to work on the creature (like a weapon's flaming ability, or charges from a wand) then it shouldn't.