3.2 Informal Sources of Presidential Power
3.3.2 Limitations on Presidential Power
1.3 The Main Characteristics of US Federalism
On 10 August 2026, President Trump signed an executive order in the Oval Office instructing the federal government to overhaul its childhood vaccination advice. According to the accompanying White House fact sheet, the order recommends that all children be immunised against 11 diseases, down from the 18 recommended by the Centers for Disease Control and Prevention in 2024. Other vaccines, including those for RSV and hepatitis A and B, would be advised only for children judged to be at higher risk. The order also proposes splitting the MMR vaccine into three separate injections given at separate appointments, and directs the Justice Department to examine state exemptions from school vaccine requirements.
Trump linked the changes to autism, a connection repeatedly investigated and rejected by researchers and one that professional medical bodies say has no credible evidential basis. He was joined by Robert F. Kennedy Jr, the Health and Human Services Secretary, whose department has pursued comparable changes since a presidential directive in December. A federal judge stayed that earlier attempt in March. Criticism was not confined to Democrats: Senator Bill Cassidy, a Republican physician who had voiced doubts about confirming Kennedy, argued publicly that presidents lack the expertise to make such determinations.
The order’s limits are structural. An executive order directs the federal bureaucracy; it is not legislation and cannot bind state governments. Compulsory vaccination for school attendance is a state responsibility, exercised under the powers the Tenth Amendment reserves to the states. That is why the order advises states to revisit their laws rather than instructing them, and why the Justice Department’s role concerns exemptions and civil rights claims rather than direct compulsion. Such federal leverage as exists is indirect, since CDC recommendations shape insurance coverage and clinical practice. Litigation is widely expected.
This is a clear illustration of the limitations on presidential power. Executive orders give a president speed and visibility without recourse to Congress, together with the ability to redirect agencies within the executive branch. What they cannot do is repeal state law or survive judicial review automatically, and both constraints are already visible here. Defenders of the order argue that federal recommendations were never binding and that an elected president is entitled to direct his own departments. Critics reply that the substance properly belongs to expert agencies and state legislatures. Either way, the outcome now rests with federal judges and fifty state capitals rather than with the White House.