The Constitution does this by setting up a system where there are three branches of government. Each of these branches has its own powers. The legislative branch cannot judge legal cases or enforce laws, for example, but no other branch can actually pass laws the way the legislature can. This is separation of powers. At the same time, however, each branch has ways that it can share in the power of the other branches. For example, the president has a part in the legislative powers because he (or someday she) can veto bills. This sharing of power is checks and balances.