Such an illegal act should not be treated lightly.

这样的违法行为不可等闲视之。

Law evasion is an illegal act.

法律规避是一种违法行为。

What you did is an illegal act.

偷东西是违法的。

He called it an unprecedented illegal act.

他说，这是史无前例的非法行为。

A contract cannot arise out of an illegal act.

违法行为不能构成合约。