In Ender's Game why can the government do away with the rule that there can be only two children per family?

Answer 1

The government is in charge. They can choose when to enforce their own laws, and when it is in the 'best interest of humanity' to bypass them.

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I'm leaving the original answer.. and adding my own. I believe you are referring to the ending of the law at the end of Ender's Game. The answer is fairly straightforward: it was no longer needed. After the Third Bugger War, which later became known as the War of Xenocide, humanity had dozens of worlds available to settle, which alleviated the overpopulation worries (though, in reality, the reason was never about overpopulation, which comes out in one of the short stories in First Meetings

I highly recommend reading all of the books in this series. In order of publication, for the most part, they are:

Ender's Game

Speaker For The Dead

Xenocide

Children of the Mind

Ender's Shadow

Shadow of the Hegemon

Shadow Puppets

Shadow of the Giant

Ender in Exile (this is set between Ender's Game and Speaker for the dead, but read it last)

There are also several short stories. Most of these are chronicled in First Meetings. They are mostly prequels to Ender's Game about his parents, though one is about his meeting with Jane. I recommend reading it after Ender in Exile. Also, a new novella (I think) in the Shadow chronology is out or coming out this year. There is also to be a new novel on the chart I saw called Shadow's Alive which appears to bring the two story lines back together, which should be interesting considering the 3000 years between them at that point. The other novels are all well worth reading.

I always thought it ironic that Ender became known as the Xenocide. The irony became that much grater after Card wrote Ender in Exile, which covered how that came to be, though I suspect it was inevitable in any case.

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Answer 2

In the novel "Ender's Game" by Orson Scott Card, the government implements strict population control policies as a response to the ongoing threat of alien invasion. Allowing families to have more than two children is a necessary measure to ensure a strong military force and a more efficient breeding program for potential military leaders like Ender Wiggin. The government prioritizes the need for exceptional individuals, like Ender, to be born and trained to defend against the impending enemy attack.