In its attempts agains depopulation, the government issues new rules to encourage people to have more child. But childbearing is not —————— .
I want to say that childbearing is not a matter of order, that is, people cannot be forced by rules to have more children: to impose such laws would be to breach basic human rights.
Is there any word, idiom or phrase to say that something is not a matter of order?
Not a matter for order - my first thought was not a matter for regulation, or not subject to regulation, or perhaps cannot be regulated. But of course China famously regulated the number of children per family for some years by limiting how many children couples could have.
Cannot be forced and cannot be compelled both sound as if they are closer to what you want to say in this context.
Another possibility would be children cannot be produced to order. Here produced to order has the commercial meaning that goods are ordered by a customer from a supplier who makes them as they are ordered (instead of filling the order from a stock of standard items).
Childbearing is not a statutory matter.
Cambridge
statutory adjective:
decided or controlled by law
More precise but longer
Note: "Order" cannot be used in the context of directives issued from a government. Although governments laws asking a people to do various things are of the nature of order, as in the military, for example (obey orders), in the context of goverment and the people that depend on it the term "order" is not idiomatic. However, a government might give orders to its armed forces. If you mean "order" as in "to maintain order", then this is not right either for the context of your paragraph.
Without using negation, a word that works is voluntary.
... childbearing is voluntary.
Google dictionary (Google search for "define voluntary"):
voluntary adjective
- done, given, or acting of one's own free will.
"we are funded by voluntary contributions"
