Which action occurs in a presidential government but not in parliamentary
government

Both presidentialism and parliamentarism are unequivocally democratic, but each of these regimes leads to different political consequences.

The great difference is that in parliamentarism the executive branch is composed of a president or a monarch, head of state, with limited powers, and a government appointed by Parliament, which at any time can censor. In presidentialism, however, the head of state and government coincide in the same person, are not subject to parliamentary censure and the Legislative Branch is limited to the area of law making.

Therefore, in presidentialism, voters elect the head of government (who in turn is head of state); instead, in parliamentarism, the head of government is appointed by the head of state, who is voted by the people.

a case involving the laws of a single state.