Ummmm... that's checks and balances, Leoba. Another term for the same thing is separation of powers, which is kind of misleading though, since it's not really a separation of powers, but a working together of powers, and thus controlling each other.
What I meant was that the veto thing is pretty much an executive thing, as in, the President's veto to a bill of law (for example), and rather uncommon in legislature. A single member of parliament couldn't stop a bill from becoming law, for example, since legislature usually works on a majority principle.
*sw00nz for Age of Empires*