In the brief time since taking office, President Trump has issued important Executive Orders and Presidential Memoranda - see White House Presidential Actions. The United States Constitution Article 2 vests the executive power in the President.
Executive Orders issued by various Presidents may be seen via the Federal Register.
A useful explanation of Executive Orders is available at CNBC - Executive Orders: what they are and how they work
Links of interest:
International Bar Association 10th December - Open letter calls on President-elect Trump to address declining human rights in the United States
The Advocates for Human Rights responds to White House Executive Orders on Immigration