If an employer wants to dismiss an employee for cause the employer is required to provide the employee with written warnings, unless the employee`s conduct is so extraordinary that immediate dismissal is warranted.
As this was not the case then your nephew should consider a claim for wrongful dismissal and seek damages from his employer.
Generally the damages would be equal to what he would receive had he been dismissed without cause. If that had been the case he would have been entitled to receive "reasonable" notice or pay in lieu of notice.
Generally, in determining what is reasonable notice Courts look at several factors including the length of time your nephew worked for the employer, his age, position, the likelihood of finding new employment etc.
At the high end, if your nephew were in a managerial position, the Court would likely order one month's notice or pay in lieu of notice for each year of employment. If he were not in a managerial position the Court would order somewhat less.
Does that help as a starting point?