A case involving four former officials of the Federal Emergency Management Agency is about to come to trial here, and it could have an impact on the job rights of federal political appointees.

The former regional directors filed suit nearly two years ago, claiming that they had been fired by the Reagan administration solely because they were Democrats.

The administration contends that they were removed for other reasons, but it argues that no matter what the reason was the firings were legal because the officials were non-career Senior Executive Service employes.

When Congress created the SES it designated two types of federal executives: career civil servants, who are protected by Civil Service laws and generally have worked their way up the ranks, and non-career senior executives, who don't always have government experience and who serve "at the pleasure" of the president. There are about 600 non-career SES employes in the government now, in addition to 1,600 so-called Schedule C political appointees at GS-15 and below.

In their suit, the former directors cite a 1980 Supreme Court decision, Branti vs. Finkel, which they say gave political appointees new protections. In that 6-to-3 ruling the justices said politicial appointees could not be fired for political reasons by a new administration unless "the hiring authority can demonstrate that party affiliation is an appropriate requirement for the effective performance of the office." The case involved state employes in a New York county prosector's office.

FEMA officials claim that the directors, all of whom were appointed by President Carter, were removed for a variety of reasons, not just for being Democrats. But depositions have raised questions about some of the administration's charges against them.

In one case, the government said it fired Charles T. Johnson, a veteran civil defense and emergency manager, and replaced him with a Republican real estate agent who had no experience managing disaster relief, because Johnson had "completely fouled up" the government's response to the Three Mile Island nuclear emergency.

The government later retracted the charge after Johnson pointed out that he didn't work for FEMA when the nuclear accident occurred.

The government also has stated that Bernard Gallagher, the acting FEMA administrator who fired the officials two weeks after President Reagan took office, had never worked with them, interviewed them or reviewed their personnel files. He sent White House counselor Edwin Meese III a memo that identified the directors and their proposed replacements almost exclusively by political party affiliation.

The Justice Department argues that it doesn't matter why the directors were fired because they held "political jobs." It contends that the regional directors often met with the press and with regional, state and local public officials to discuss disaster aid. In such cases, it said, they represented the president and had to be attuned to his philosophy.

The former directors argue that they were managers, who simply were supposed to follow orders and procedures spelled out by headquarters in Washington. Making the directors "political policy-makers" would be dangerous, they say, because that might encourage them to dispense federal disaster aid according to political considerations.