If you are being told to show up at a specific time and are directed as to what work to do, then it is likely that you are being misclassified as a 1099 contractor, and are really a w-4 employee - and should be paid from the time the employer requires you to be at work. It also means that the company you are working with is, even if they classify you as a 1099 contractor, still legally responsible for paying taxes on your wages, and deducting taxes from your wages.

The IRS has a very simple and straightforward test that explains the difference between a contractor (1099), common-law employee, statutory employee and statutory non-employee are.

From your description you are a common-law employee.

You are NOT an employee so labor laws do NOT apply to you

you are a contractor and your payment agreement is between you and the business........

most likely you are NOT legally an independent contractor but that is a totally different issue.

many if not most independent contractors are mis-classified, and are actually employees, but i digress........

EDIT:

you do not understand the concept of an independent contractor if you think the law covers you... this is directly from the state of California:

Q. Does it make any difference if I am an employee rather than an independent contractor?

A. Yes, it does make a difference if you are an employee rather than an independent contractor. Californias wage and hour laws (e.g., minimum wage, overtime, meal periods and rest breaks, etc.), and anti-discrimination and retaliation laws protect employees, ************but not independent contractors.**************

Additionally, employees can go to state agencies such as DLSE to seek enforcement of the law, whereas independent contractors must go to court to settle their disputes or enforce other rights under their contracts.

http://www.dir.ca.gov/dlse/FAQ_Independe¦

If they are a legal employer then, yes, they are required to pay you for that time. However, do you have proof that you were there at 3:00? (signed paper, a couple other employees who saw you) If not, I don't think you can take action. If you do, try contacting the Labor Relations Board. I provided you with a website, you can find all the information on there.