Courtroom combat: Inside the federal judiciary system where Trump's agenda is under assault

The legal resistance to President Donald Trump’s second term is in full swing with more than 120 lawsuits filed since Jan. 20 by states, advocacy groups and individuals targeting his executive orders and policy agenda.

As the lawsuits move through the judiciary, understanding the structure of the federal court system can help clarify how these challenges are likely to unfold.

Article III of the U.S. Constitution establishes the Supreme Court along with "inferior Courts as the Congress may from time to time ordain and establish." The Constitution also states that judges shall hold their offices during a period of "good behavior."

The federal judiciary has three main levels: district courts (trial courts), circuit courts (the first level of appeal) and the Supreme ...