The actual text of the Constitution is the final and absolute yardstick all laws are measured against. When the Supreme Court considers the constitutionality of any law it must measure the law against the original text of the constitution and its plain meaning when it was written.
Notice of working hours/changes. Your employer must give you reasonable notice of any changes to your working hours, such as cancelling your shifts. They may request last minute changes (such as ringing you that morning to say that they do not require you to work) and you can choose to agree to this change.
If notice of a temporary schedule change is not given to the employee by Wednesday of the preceding service week, the employee is entitled to work his or her regular schedule. Therefore, any hours worked in addition to the employee's regular schedule are not worked instead of his or her regular schedule.