If you work in an at-will position, your employer can terminate you, demote you or decrease your salary at any time and for any reason, according to the National Conference of State Legislatures. Many employers make you sign an at-will agreement when they hire you to avoid any legal problems that can arise from salary disputes or termination.
There are a wide variety of reasons why you may receive a salary decrease from your employer. Generally, it is an overall reflection of the health of the organization and how well you are performing in your current position. If the company does not have the money to pay you, they may offer you less money or let you go. If you are not performing to the company's standard, they may lower your pay, so it is commensurate with your performance.