Q: Concerns regarding wrongful termination of employment

A: Yes, he can. I don't see the state in which you work, but here is the way employment works in the United States. For about 150 years, the United States has been the only industrialized country that has continuously had "at-will" employment. In other countries, employers must have a good reason to fire employees, provide notice or give severance pay (or provide some combination of these employee benefits). In the United States, as a general rule, employers can fire employees for any reason. Many people find this surprising as they think the employer has to be reasonable or have a good reason.

The first exception to the at-will rule was made in 1959 by a California court holding that an employee could not be fired for refusing to commit perjury on behalf of the company. Since then, courts and legislatures have carved out numerous exceptions to at-will employment. In 1964, for example, Congress passed Title VII of the Civil Rights Act. This law prohibits employers from discriminating against employees because of their race, color, religion, sex or national origin. Congress subsequently passed other laws prohibiting discrimination on the basis of religion, physical or mental disabilities, veteran status, genetic information or citizenship. States and cities have passed their own laws as well.

But "at will" is still thought of as the default and employers may fire you for being too late in getting a drug test back to him or for simply no good reason at all (say, you are a Giants fan and the employer is angry that the Cowboys lost).

With that said, you may still want to briefly talk with an employment lawyer or email them to confirm. There may be other facts that you have not mentioned. But, based on what you have written, he can fire you for that reason.