If you do not have an employment agreement for a specified term (ie 1 year), then your employment is probably at-will. California law provides that employment is at-will so you can be hired, fired, demoted, or promoted at any time, for any reason, or for no reason at all. One employee’s pay can be reduced without reducing other employees’ pay in the same position, so long as the employer did not discriminate in his/her selection. For example, if your employer selected you for a decrease in pay because you belonged to a protected class, that would not be in compliance with the law. The employer may have used selection criteria other than length of service when making the determination. Selection criteria can include hard skills such as knowledge of the subject matter, attendance, punctuality, or skills such as ability to communicate, teamwork, attitude, attention to detail, reliability, or leadership skills. You can ask your employer why you were the only employee to receive such a pay cut and see if your employer has any feedback for you.