HAS PRESIDENT REAGAN done something extraordinary or even scandalous by granting a pardon to Eugenio Martinez, one of the Watergate burglars? He has not, for while presidential pardons are not granted automatically or even easily, they are by no means unusual. Nor is this situation at all similar to the granting of a pardon to former President Nixon before he had been charged with any crime.

The Constitution gives the president power to grant "reprieves and pardons for offenses against the United States." President Ford's pardon of former President Nixon was an unusual and controversial--though legal--exercise of this power because it was granted without consultation with any other government officials and before Mr. Nixon had even been charged. The pardon effectively precluded any prosecution for crimes committed while Mr. Nixon was in office.

Most pardons, including the one granted to Mr. Martinez the other day, are granted only after conviction, after sentence has been served and fines paid and after the petitioner has demonstrated that he has lived as a good citizen for a considerable period of time. Applications are not even considered until five to seven years after the sentence has been completed. The Justice Department conducts a full field investigation in every case, and the president acts upon the recommendation of the Pardon Attorney, an official of the department. Mr. Martinez has met these tests; other Watergate offenders who have sought pardons have not.

A pardon does not reverse a conviction or expunge a criminal record, but it does restore basic civil rights such as the right to vote, to serve on a jury and to hold public office. In the case of certain professionals, such as lawyers, a pardon is usually required before a license to practice is restored. More than 500 petitions for pardon have been filed since President Reagan took office, and 175 have been granted.

Eugenio Martinez, a bit player in the Watergate drama, was convicted of conspiracy, burglary and wiretap offenses, and he served 15 months in prison for those crimes. He was paroled in January 1974, and has lived and worked quietly and without incident or offense since that time. A pardon simply acknowledges these facts and encourages an offender who has paid a penalty and changed his ways to get on with his life. The process is designed to bring compassion, hope and incentive to those who have erred but reformed. We see no scandal here.