になっている vs がある ？

Question

I found a sentence from my study book.

It said:

このマンションは動物を飼ってはいけない規則になっている

Why is it

になっている

and not

がある ?

Is it replaceable?

Answer 1

To answer your question, I think that it would be good to review the V + ている conjugation.

A lot of the time we are taught that V + ている means "verb-ing." For many cases that is correct. However, there are some cases where "verb-ing" is not 100% accurate as far as translation goes. For example, 死{し}んでいる does not mean dying, but dead.

In my time in Japan, I spent a bit of time going door to door as part of my work. Quite often, the person answering the door would say:

主人{しゅじん}は仕事{しごと}に行{い}っています。

In the morning, translating this as My husband is going to work would make sense, but it doesn't make as much sense at 4:00PM. This is because translating 行{い}っている as going isn't correct. Rather, you should translate it as has gone to __ or is at __. Long story short, you would translate it as:

My husband is at work.

For more information, please see this webpage. I really like how it describes the meaning of V + ている in terms of resultant states. We are dealing with a resultant state in this situation. To use their words:

If the verb indicates an instantaneous change of state or transfer, then the て- form + いる (iru) will express a resultant state.

Like 行{い}っている (has gone to/is at) or 死{し}んでいる (is dead)。

---

Become (なる) is another one of those cases. You cannot translate it as becoming, as that would not be correct, but rather translate it as it is established or it is the case that.

このマンションは動物{どうぶつ}を飼{か}ってはいけない規則{きそく}になっている

It has been established that keeping pets at this mansion is not allowed.

Why not ～がある？ Well, in terms of overall meaning you could replace ～になっている with ～がある、and have it carry almost the same meaning (I wouldn't do it though). This is not just a question of style/formality, but also a question of meaning. It's not as formal to say ～がある, and it means something different.

Just to be clear, this does not mean ～がある ＝ ～になっている。That is false, as the meanings are different. It just happens to be the case that you could rephrase the sentence with ～がある and carry a similar meaning. Here is an example to drive this point home:

わが家{や}では、お箸{はし}を使{つか}わず、手{て}で食{た}べることになっている。

In our home, we don't use chopsticks, we eat with our hands.

Setting aside the peculiarity of this sentence, if we were to replace ～になっている with ～がある、we would have a different sentence. Eating with your hands in that home is an established thing. When I say established, I mean that things are always that way. It's a tradition, not a one-time deal.

If we were to say:

わが家{や}では、お箸{はし}を使{つか}わず、手{て}で食{た}べることがある。

In our home, there are times when we don't use chopsticks and eat with our hands.

There is no sense of establishment. This isn't a tradition, it's more of a fling.

---

So, bringing it all together, the reason they use ～になっている in your sentence is because the rule (規則{きそく}) is established. It's not just a thing that happens. There is a sense of permanence and there is an expectation that you will abide by that rule.

If you were to say ～がある、you would get the feeling that there's a rule that pets aren't allowed, but not everyone follows the rules. So while you would get almost the same meaning, they are in fact different.