Although your status as a government or non-governmental employee does not matter for the purposes of whether you can bring a civil action in federal court, it does matter for the route you take to get there.
Non-federal employees must generally (with exceptions for age and other exceptions) contact the Equal Employment Opportunity Commission (EEOC) first before receiving a right to sue letter that will allow them to file a civil action in federal court.
Federal employees, on the other hand, have to completely different process altogether that involves the EEOC or the MSPB being involved in a different manner than private sector litigation. The video below discusses this process for federal employees.
Regardless of your status as a federal employee, a discrimination civil action may eventually be brought in federal district court, entitling you to the ability to subpoena and depose witnesses, obtain evidence, and possibly have your day in court.
If you feel you've been unfairly terminated, contact an employment attorney to discuss whether you have any remedies.