Government comes in many forms and derives its powers in several ways. In many cases, authority comes from federal or state constitutions. For example, the powers of the presidency are specifically outlined by the Constitution of the United States of America. Under American common law, court rulings can become part of the law of the land. As a result, there are instances when legal authority and powers are given through the judiciary. Then there are statutory powers which make up the largest part of the body of law.
Statutes are laws. In the United States, law are created and passed by the legislatures, including the federal legislature --- Congress --- and state legislatures and assemblies. Bills become laws when an executive --- the president or a governor --- signs them. If an executive refuses to sign a bill into law, then the legislature can still make the law valid by supermajority vote known as a veto-override. In the case of the federal government, this requires three quarters of both the House of Representatives and Senate.
Statutes can do many things, including creating budgets, criminalising behaviours and developing new forms of governmental agencies. When a statute creates a new agency or governmental position, it usually gives legal authority. For example, when Congress created the Social Security Administration, it gave the director the authority to run the agency in accordance with its mission and within guidelines prescribed by Congress. Similarly, Congress and the president created the United States Citizenship and Immigration Services (USCIS) and gave it the authority to control and oversee immigration and visa issuance.
Referenda and Initiatves
Some states, including California and Washington, give statute-making authority directly to the people. Referenda, initiatives and propositions allow voters to consider a potential piece of legislation and to vote on it in the course of elections. Voter-passed legislation can also include statutes ascribing authority. For example, an unincorporated section of a county may vote to create its own city and issue powers to a mayor and police chief. In another example, residents of a school district might vote to levy a tax upon themselves to increase school funding. They give statutory authority to the county tax collector to increase taxes.
Statutory powers can be trumped, vacated or nullified by a court ruling. Not all statutes are constitutional. If an application of an unconstitutional statute comes before a court, judges have the authority to overturn the statute. Additionally, counties cannot pass laws that contradict their state statutes and states cannot contradict federal laws. When contradictions occur, courts have the responsibility to strike down improper statutes.