I wrestle with this myself, see the related question How do you help players not focus on the rules?
There is a tendency among people to start Pharisaically treating any body of rules as the end in and of itself and not the means to the end. Combined with a sense of rules entitlement fostered by both computer gaming and RPG Organized Play campaigns, it can generate a situation where people are affected by the "when all you have is a hammer, everything looks like a nail" syndrome and the only options considered are ones where there's rules for it. Warning sign: People poring over their character sheets trying to figure out what to do next instead of thinking about the situation and engaging with the world to decide what to do next.
Choice of Game System
This behavior does somewhat correlate with detail of the game system. I play a lot of Pathfinder, but frankly am displeased with how the large amounts of rules coverage contribute to the syndrome you state. One of our DMs is very rules-oriented and always feels constrained to follow, for example, whatever mini ruleset an AP has for a subject over what might make sense in-world, and it bothers me when that happens - because I care less about "rules" and "winning" and more about immersion in a realistic fantasy world. You can go for rules-lighter game systems to mitigate this, though I have seen the same rules lawyering/"don't try anything there's not an explicit rule for" even with much lighter systems like Savage Worlds. Not saying a lighter system can't help, but there's also a mindset component to be overcome.
Same thing with storygames - many people will cite them as the solution but frankly most of them are gamist/narrativist and are as rules-constrained in their generation of story as any big ol' trad system.
Use of Game System
The best answer to my own "focusing on the rules" question was the one where @valadil suggested telling everyone you're running your own game, loosely based on whatever the ruleset at hand is. IMO it should always be the GM's prerogative to interpret, transform, or ignore the rules as it best suits the game.
Because to be honest, game designers are not gods. RPG rulesets are neither magical nor scientific. It's just junk some other geek wrote down; someone whose opinion on the Avengers movie you would doubtless find heretical were you to meet them IRL. Paying $30 for it doesn't make you the rulebook's thrall. Players do need some consistency to feel in control of their character - but a good GM can make that consistency the reality of the game world and not the rules in the book.
You have to make sure you're using that ability "for good" and not to arbitrarily mess with the players (or have them feel like they're being messed with because you're not communicating your mental picture of the game well and theirs conflicts, so you rulings seem unfair to them). But then you can freely use the rules as guidelines, bring analogous rules to bear on new situations, assign bonuses/penalties as you see fit, and breaking them when it makes sense.
Outside the Game System
Often players have reasons for falling back on the game rules. They give them some hope of success. As GM, you have to make sure you are not discriminating against "non-rules" prescribed choices, because if you are, you are implicitly telling them to live and die by the rules.
The one game that helped me break out into a new level of gaming was Feng Shui, the game of HK action by Robin Laws. It suggested bonuses, not penalties, for cool undefined actions and playing more fast and loose with the rules (no tactical maps, let the players narrate a little). It really helped me and my gaming group break out from the rule-mindset we had gotten into and become a lot more freewheeling, and the techniques port right back over to other games.
In fact, while running Feng Shui I had luck with inverting the new softie-GM saws of "always say yes" or "say yes or roll the dice." I said "If you ask me, the answer's no. Just do it. If you ask me if the helicopter's skid is still low enough that you can jump up and grab it I'll say no; if you say 'I run and leap to grab the helicopter's skid' then great, roll it." (Unless of course it's patently impossible at your game's power level.) After a couple cases of me telling people "No, because you asked," suddenly everyone's much more comfortable operating outside the options specifically enumerated by the rules. The reason this is successful is basic psych. When you game feeling constrained by the rules, the rules empower you but when you go outside them you feel like you're always playing "Mother may I" with someone, which is disempowering. If you are explicitly empowered to try inventive things, to the point where you are discouraged from even thinking you have to ask permission, then you gain the confidence that you were using the rules as a crutch for previously.
Conan doesn't ask if he can leap up on Dagon's back and tear his horn out; asking is for women and Shemites. He just does it.
I found after running/playing Feng Shui that even when we went back to other games, we took a much less rules-constrained approach after that experience.
Make your players feel empowered when not "covered by" the rules, and have an agreement with them that the game world's reality should come first. The rules are a helpful scaffold for this but, like any scaffold, at some point it's got to come off.