A few weeks ago, I was asked on IRC whether it was appropriate to deviate from the new Guide to Fixing Common Play Errors. My tongue-in-cheek response was "Deviate like hell," a line that obviously got a little bit of play on the internets, and my joking attempts to suggest there was actually a comma in there fell on deaf ears. There's actually a lot of truth to the statement, and understanding it helps to illustrate the difference in goals between Regular and higher Rules Enforcement Levels, and whom the documents are written for. You will deviate a lot more at Regular REL, and as long as you're deviating for the right reasons, it'll produce better tournaments. My goal here is to give you some guidelines that will help you understand when it's appropriate.
At Competitive and Professional levels, consistency of rulings is very valuable. That universe consists of a set of players who will travel to larger tournaments, and often experience rulings from different judges. In order to ensure that they have the same experience wherever they go, we strive to keep rulings the same.
This does not come without cost. The Infraction Procedure Guide, even after an effort to streamline it, weighs in at a hefty 26 pages of fairly technical information. It's daunting for people who have studied the rules of Magic; for those without that knowledge, it's impenetrable. We cannot expect non-judges to read it, and even many who have passed the test may not understand the nuances. This is fine, and it's why we give powers of deviation only to the Head Judge of these events, under the assumption that they'll understand the underpinnings of policy well enough to make a necessary ruling.
This model does not work at the store level, though. The 'Head Judge' of the tournament is likely to be the person behind the counter who happens to be working that night. If you're lucky, the local Rules Guru has shown up and will be dragooned into the role. Expecting them to make consistent rulings based on a lengthy document they've never read (and likely don't want to) is impossible. Fortunately for us, consistency at the store level isn't the top priority. Most of the players will never leave the store, and, with the possible exception of Prereleases, won't interact with a diverse set of judges.
Instead, we have the Guide to Fixing Common Play Errors. It isn't a structured system for making rulings—at two pages, how could it be? Instead, it's a set of principles and simple recipes that can help a Head Judge get through a ruling with only a little bit of Magic knowledge. The barrier to reading it is minimal, and, frankly, there's nothing wrong with posting a copy on the wall of the shop for all the players to see.
It's two pages long. And many of you reading this will be acutely aware that two pages isn't enough to encapsulate all the things that can go wrong in a game of Magic. Blindly applying the Guide can lead to some really strange situations.
If the Guide result seems counterintuitive, consider alternatives
The Guide was written by some very smart people. In many cases, it'll produce an intuitive result. Intuitiveness is a really important part of Magic. The Rules team spends an incredible amount of time making the rules work so that they match what players expect to happen, and in the modern era, you can get a long way just by ruling intuitively. Most of the wordiness of the IPG is devoted to making intuitive things happen as much as possible. The Guide lacks all that extra text, so trying to follow the two sentences it devotes to each infraction to the letter is going to occasionally cause weird results. Don't do that—if the result seems wrong and you can see a better solution, it's appropriate to deviate. It's a guide, not an instruction manual. Fairness is more important than accuracy.
If both players agree on an outcome, it's correct
Consistency is important to Competitive tournaments. What's important to Regular tournaments? Customer service. If both players are happy with a solution, it is, by definition at Regular REL, the correct solution. Use it.
Consider that players do this all the time. Many thousands of words have been devoted to the appropriate penalty for a player who doesn't exile a creature hit by Path to Exile. What happens when they realize it a turn later at Regular REL? The players pull the creature out of the graveyard and the game goes on. You'll almost never hear about it. If they do call a judge, and both seem happy with the fix, what's the point of trying to get technical on them?
Similarly, if you can see a fix that isn't an exact match for the Guide, but is satisfactory to both players (though they may not be entirely happy with it!), that's appropriate.
Obviously, if you feel that one player has been coerced or talked into a solution or doesn't understand the relevant rules, you may need to intervene. That can sometimes happen if there's a disparity between how the players are playing the game. Which brings me to the next principle:
Don't let the rules lawyers have their way
There's a place for rules lawyering in the game of Magic. Somewhere. That place is definitely not at an FNM, where little Timmy is playing in his second event, and kind of has combat down now.
What is a rules lawyer? A simple definition is that a rules lawyer is someone who attempts to use the minutia of the rules or the ambiguity of communication to trap the other player into doing something they didn't think they were doing, or to prevent them from doing something that they are trying to do. If you look at many of the shortcuts in the MTR, they are designed to stop this. Of course, many judges at Regular REL events will not have read the MTR, so we fall back to the underlying principles - if it looks like rules lawyering, it probably is, and it's not something we want to encourage at friendly tournaments.
Again, this comes back to Customer Service. Little Timmy is super-excited about this new game, and what kind of impression is he going to get when his opponent twists his words to make him do things he didn't intend to? Even if he's an experienced player, losing on a weird technicality is going to be a poor experience. Players need some protection, and it needs to be clear to the rules lawyer that his expectations don't match the expectations of a Regular REL tournament.
Don't turn to the IPG
One final anti-guideline: many of you are super-smart judges, who have committed the entire IPG to memory and understand the principles behind it. And the IPG has lots more details that it's tempting to try to use. Don't. The IPG is written for a Competitive and Professional tournament environment and many of the remedies are too harsh for Regular REL. If you like a fix that falls under the criteria above that just happens to match something in the IPG, that's fine, but don't try wedging IPG solutions into your events.
Unlearning things is difficult. It will be tempting to use all your extra knowledge to make a 'correct' ruling. But not doing this is the price you pay to be allowed to "deviate like hell" in the service of your players.