R is for Rules
Without rules, an evening of Dungeons and Dragons would play out more like a child’s game of cops and robbers. Lots of pointing of fingers and a back and forth argument over who hit who. The rules provide a framework that allow combat, or any action with a risk of failure to be decided by a roll of the dice.
Unfortunately, the rules can’t cover every possibility, leaving room for some discussion or arguments about how to interpret the rules. Under most circumstances, I tend to make a ruling as Dungeon Master, and then if there is need for further discussion, it happens after the game. This allows time to have an in-depth discussion without breaking the flow of the game session with a lengthy discussion. It also lets the player and DM do a little research online to see how other DMs interpret the same rule. If the discussion and research lead to a change in the ruling, I generally don’t go back and change things unless the ruling resulted in a significant loss like a character death, or loss of an important piece of equipment. We simply use the new rules interpretation during future sessions.
This method works well with a group that games together on a regular basis. Because they are interpretations of the rules rather than changes to the rules, these rulings are not truly house rules. Collected they do make something of an addendum to the rule books, and can be added to the list of house rules to be given to any new players joining the campaign.
In a convention setting, or other one-shot event it’s usually best to allow the DM rulings to stand. I’ve seen some players in this kind of setting refer to rulings, or FAQs found online, and it is up to the DM to decide how to handle this, but it’s sometimes difficult to keep up with every ruling, or rules change made online. While the Internet is a great reference source, in the short time allowed for these types of events there isn’t enough time to spend debating the rules.
No matter what the situation, the DM is the ultimate interpreter of the rules, though of course if one is draconian in their rulings they’ll likely find themselves gaming alone.