What limitations do historians face when trying to determine causation

The principal limitation is time.

Explanation:

Historians study chronicle events that happened once. The fact that they can't go to the past to prove their hypothesis is a big problem.

That's why causation is a real problem to social science. Because other sciences, like physics for example, can establish causations by an experiment that they can perform any time, this scenarios allows sciences to manipulate variables in their studies. In social science manipulation of variables is lacking because in the best of cases you're gonna study people.

arresting and exicuting citizens

both include an amendment process.