"becomes obligatory" is a correct and usable phrase in written English.
It is used to describe something that is required or necessary, often due to a rule or law. For example: "It becomes obligatory for all employees to wear a mask while on the job."
From the sixth book onward continuo support becomes obligatory, and in consequence solo voices emerge from a choral background with tremendous dramatic effect, especially in the later works.
On the nuttier fringes of the conversation are those who claim to believe it will come to be seen as the first move in a new oppression which will end only when wearing the burqa becomes obligatory.
Couples are ideal for getting patients to resent the very individuals they most desired to show charity: In discussing any joint action, it becomes obligatory that A should argue in favour of B's supposed wishes and against his own, while B does the opposite.
At 18 voting becomes obligatory, so the candidates' task is less to get out the vote than ensure the voters tick the right box, says Alexandre Bourgeois, Mr Neves's social-media wonk.With that in mind, Mr Bourgeois has dispatched scouts to São Paulo's poor periphery to identify teenage movers-and-shakers, some with hundreds of thousands of Facebook followers.
But functional requirement becomes obligatory.
Although in the past complicated and often considered 'exotic' process, hot stamping of steel is now widely used in the automotive industry and for some safety components it becomes obligatory.
Still, certain conventions become obligatory over time.
But things don't become obligatory.
Mr Rauch's book should become obligatory reading for all.*In 1995-96.
It appears to have become obligatory to describe Dubuisson as enigmatic.
So the stylistic character of SMS writing changed, and texting abbreviations, previously optional, became obligatory.
