Admission is by invitation only.

凭请柬入场。

《牛津词典》

Entry to this competition is by invitation only.

此次竞赛的参赛只凭邀请函。

《柯林斯英汉双解大词典》

You can also start a public group with invitation-only access, allowing you to control membership by having users request to join.

也可以发起一个只有受邀请的用户才能加入的公共组，这样可以通过让用户请求加入来控制成员资格。

youdao

But on his only mission to the region, earlier this month, he did not get an invitation to visit Pyongyang.

VOA: standard.2009.03.25

MoviePass is currently invitation only with general availability of the service to be announced in the near future.

ENGADGET: MoviePass launches iPhone app and card combo, takes unlimited viewing to all US theaters

In fact, close to 70 billionaires from 20 countries were expected to attend the invitation only event this year.

FORBES: The Richest Men At Davos

Participation in the OnStar Family Link pilot is by invitation only and will include approximately 10, 000 active U.S. OnStar subscribers.

ENGADGET: OnStar Family Link brings loved ones closer together through vehicle tracking