In the United States, state corporate law determines most questions of internal corporate governance - the role of directors; the allocation of authority between directors, managers, and shareholders; etc. - while federal law governs questions of disclosure to shareholders - annual reports, proxy statements, and periodic filings. Despite substantial incursions by Congress, most recently with the Sarbanes-Oxley Act, this dividing line between state and federal law persists, so state law arguably has the most immediate effect on corporate governance outcomes.
Pritchard, Adam C. "London as Delaware?" Regulation 32, no. 3 (2009): 22-8.