kono houritu ha zyuuyou desu.

It is read:

この ほうりつ は じゅうよう です。

In normal Japanese writing, it would usually appear without spaces:

この法律は重要です。

No. Japanese normally does not use spaces between words.

The spaced version is often used in beginner materials to make the sentence easier to read. In natural writing, you would normally see:

この法律は重要です。

この means this, but it must be followed by a noun.

So:

• この法律 = this law

Japanese demonstratives like この / その / あの come before the noun they modify.

Compare:

• この法律 = this law
• その法律 = that law
• あの法律 = that law over there

You cannot normally say この by itself as a standalone pronoun. If you want to say this by itself, you would usually use これ.

法律（ほうりつ） means law in the legal or formal sense.

It is a noun.

So in this sentence:

• この法律 = this law

When は is used as the topic particle, it is pronounced wa.

So:

• 法律は is pronounced ほうりつ は in writing, but spoken as ほうりつ わ

This is a standard feature of Japanese. The same kana は can be:

• ha when it is part of a word
• wa when it is the topic particle

は marks the topic of the sentence.

In この法律は重要です, the topic is この法律 (this law). The sentence is saying something about that topic:

• As for this law, it is important.

A very literal breakdown would be:

• この法律 = this law
• は = topic marker
• 重要です = is important

So the sentence is presenting this law and then describing it as important.

Japanese does not always work like English here.

In this sentence, 重要です functions as is important.

• 重要 = important
• です = polite sentence ending / polite copula

So Japanese does not need a separate word exactly matching the English is in the same way English does.

That is why:

• この法律は重要です = This law is important.

Yes, but more specifically, 重要 is a na-adjective (also called an adjectival noun).

That matters because na-adjectives behave differently depending on where they appear.

At the end of a sentence:

• この法律は重要です。 = This law is important.

Before a noun:

• 重要な法律 = an important law

Notice the な before the noun. That is a key feature of na-adjectives.

Because 重要 is at the end of the predicate, not directly before a noun.

You use な when a na-adjective directly modifies a noun:

• 重要な法律 = an important law

But when it comes at the end of the sentence, you do not use な:

• この法律は重要です。 = This law is important.

So:

• before a noun: 重要な
• at the end of the sentence: 重要です

です makes the sentence polite.

So:

• この法律は重要です。 = polite
• この法律は重要だ。 = plain / less polite
• この法律は重要。 = very casual, often conversational

For learners, です is the standard polite form to use in most normal situations.

Yes, but the nuance changes.

• この法律は重要です focuses on this law as the topic: As for this law, it is important.
• この法律が重要です puts stronger focus on this law as the thing that is important, often implying contrast or selection: This law is the important one or It is this law that is important.

For a simple neutral statement, は is very natural.

Japanese does not have articles like a, an, or the.

Instead, Japanese uses context and words like この to show specificity.

So:

• 法律 can mean law, a law, or the law, depending on context
• この法律 specifically means this law

There is no separate word corresponding exactly to English the.

A little, yes.

English:

• This law is important.

Japanese:

• この法律は重要です。

A useful way to think about the Japanese order is:

• [topic] + [comment about the topic]

So:

• この法律は = as for this law
• 重要です = is important

Japanese often builds the sentence by first introducing the topic and then saying something about it.

Yes.

Polite:

• この法律は重要です。

Casual / plain:

• この法律は重要だ。

In very casual speech, people may also say:

• この法律は重要。

But for learners, 重要です is the safest and most standard form to use.

You would put 重要 before the noun and add な:

• 重要な法律 = an important law

This is different from the original sentence:

• この法律は重要です。 = This law is important.

So the two patterns are:

• 重要な + noun = important + noun
• noun は 重要です = the noun is important

In beginner explanations, it is often treated like the subject in translation, because in English we say This law is important.

But more precisely in Japanese grammar, この法律 is marked by は, so it is the topic.

That is why many textbooks explain は as a topic marker, not exactly the same as an English subject marker.

For practical learning, it is fine at first to understand:

• この法律は = this law / as for this law

But as you continue studying, it helps to remember that topic and subject are not always identical in Japanese.