Follow your company's disciplinary (insubordination) policy... Inform them that policy and procedures are setup in such a manner that your facility has developed them to be either more efficient, less error producing, for sample integrity, paper trail throughput.. etc..
Document, document, and document. make accurate notes on who and how and when what errors were made and by who. Any supporting statements from staff on big errors can help too.
And if that doesnt resolve the matter at hand... Ask yourself if you need them more than they need you? if not let some go... that may speak in actions to the rest that this won't be tolerated.
This may sound draconian, but, hey -- Tyrany and fear worked for the last eight years, why not try it in our local office?