You are under no obligation to buy anything.

你不必非买什么东西不可。

We should fight for what we want because life is under no obligation to give us what we expect.

我们需要为自己想要的事物而奋斗，因为生活并没有义务要给予我们所期待的东西。

I'm under no obligation to do it.

我没有义务去做那件事。

Mr Obama had no obligation to act.

奥巴马对法案本身没有义务。

Voters are under no obligation to be so gullible.

选民实在是没有义务要受这样的欺骗。