If an independent contractor works for a company who assigns him shifts, can the company cancel the assigned shifts without warning or reason and effectively terminate the relationship? Assume there is no specific clause in any contract that handles termination. Is any sort of severance or notice required?
If a contract calls for work on a shift by shift basis and doesn't contain any termination clause, the default assumption would be that the contractor can be terminated at any time without notice or severance.
But, this said, not everyone classified by the person hiring them as an independent contractor is really an independent contractor for the purposes of the law. It isn't at all uncommon for a business to classify someone as an independent contractor improperly when that person is legally an employee with all of the rights of an employee under the relevant legal definitions of an employee.
The determination of whether someone is an independent contractor or an employee is based upon the facts and circumstances of the relationship and not simply by the agreement of the parties. Few people who work on a shift by shift basis for a single firm are actually independent contractors. Most are actually employees.
Assuming the contractor is actually a contractor, cancelling the contract would be governed by the contract itself. Many contractors use non-refundable deposits and include notice periods for this reason.
If there is nothing about cancelling the contract, the company can cancel it. They would potentially be liable for damages incurred to the client because of this such as missing other paid work or non-refundable expenses. Claiming these damages would involve going through small claims court.
Note that if no work was done, the contractor is not entitled to payment for the work- just other damages suffered.