If something is statutory, it is related to or set by laws or statutes. Statutory restrictions on air pollution require drivers to have the emissions from their cars checked every few years.
You might wonder what the difference is between statutory and legal. Both are adjectives and both are concerned with the law. If something is legal, it is allowed by the law, whereas if it is statutory, it is regulated by law. In the negative, this is easier to understand. If something is not legal, the law says you can't do it. If something is not statutory, there are no laws regulating it.