This week we're going over another frequently messed up scenario: interference an obstruction! First, to clarify the terminology, interference is when a defensive play is hindered, and obstruction is when a baserunner is hindered. Two different types of calls. Let's go over interference first!
INTERFERENCE can occur in several ways (and one related instance which isn't actually interference but we'll still go over for relevance). Here's the full text of the relevant rule:
15.02 Interference is:
a. when any non fielder or non permanent object except a Referee or a runner, touches or is touched by a ball in play in fair territory. This interference causes the play to end, and runners shall proceed to the base to which they were headed;
b. when any runner on or off base intentionally touches a ball, or hinders a fielder. This interference causes the play to end, the runner to be out, and any other runners shall return to the base from which they came, unless forced to advance (see Rule 14.02e);
c. when any kicker intentionally touches a pitched ball by hand or arm before the pitch is called a Ball or Strike, or intentionally touches a kicked ball to render it foul. This interference causes the play to end, the kicker to be out, and any runners shall return to the base from which they came (see Rule 14.02e).
So in section A, we're talking about anything that isn't a permanent object like a fence, overhanging wire, batting cage, or tree. The most common incidence of this: players in another game! Since the setup of our fields puts the deep outfield in the midst of another game, it's not uncommon for a player in an adjacent game to inadvertently interfere with a kicked ball in fair territory. In such a case, the play should be called dead and all runners must stop at the base they were on their way to and no further. Definitely a bummer if you just blasted one into next week, but them's the breaks. Of note: interference is NOT called when the defensive PLAYER runs into someone, but when the BALL touches another player or non-permanent object. Intentionally throwing the ball into such an object to cause interference is unsportsmanlike conduct and should NOT result in an interference call.
A related sidebar: what about PERMANENT objects that are in play? Here's the relevant rule on that:
13.02 A foul ball is:
h. a kicked ball first touching a permanent object, such as a batting cage or fence.
I've never seen it happen, but it's possible that a fly ball on Field #3 could hit the overhanging power wire in fair territory. In such a case, the call would be a foul ball. The defense cannot catch a ball called foul in such a way for an out. This isn't specified in the rules but is clarified in the FAQs. Same thing goes for balls that hit trees, fences, nets, poles, or any other permanent objects. You can't get a ball stuck in a tree and then catch it when it falls for an out.
Back to interference! In section B, we deal with runners intentionally touching the ball in play. The ref must make a judgement call as to whether the contact was intentional. If so, the runner is out and other runners must return to the base they came from unless forced. (Note: if there are runners on 1st and 2nd and the runner on first interferes with a ball, they are out and the runner on second is no longer forced to third: they must return to 2nd base). If the contact is deemed unintentional by the ref, it is considered a deflection: the runner is out but the play remains live!
A runner may also hinder a fielder. This is a judgement call on the part of the ref, but if the ref determines that the runner intentionally hindered the fielder, even if they did so within the baseline, they should call interference on the runner.
Section C is much more rare case, and deals only with the kicker. Basically this rule prevents a kicker from popping up to the catcher and then swatting the ball away to render it foul: the kicker would be out in this scenario.
OBSTRUCTION occurs when a fielder illegally hinders a baserunner. Here's the text of the rule:
10.02 Obstruction. Fielders must stay out of the baseline. Fielders trying to make an out on base may have their foot on base, but must lean out of the baseline. Runners hindered by any fielder within the baseline, not making an active play for the ball, shall be safe at the base to which they were running. Runners may choose to advance beyond this base while the ball is still in play.
The basic idea here is you can't block the baseline, with the very important caveat that a defensive player may enter the baseline when necessary to make an active play on the ball. This is a really important rule that has player safety implications, so pay attention! If you are not making an active play on the ball, there is no excuse to be in the basepath. As a defensive player it is your responsibility to know where you are and NOT hinder the baserunners. When attempting to make a force out on a base, you must place your foot on the base and lean out of the base path such that the runner can safely reach the base. If you are just hanging out on top of second base, you are obstructing the base path and, more importantly, causing a safety hazard to yourself and the runner!
Again, all of this comes with the caveat that if you must enter the base path to make a play on the ball you may do so, so collisions that are not obstruction are still possible, but the rules seek to avoid them to what extent they can without placing an unfair burden on the defensive player.