The 'Inside Story' on guarding press freedom

''Whose news is it?'' is the important question posed by one of America's top media critics, Hodding Carter. ''Yours,'' he answers his own question. Then, Carter adds ominously, ''If you can keep it. . . .''

Inside Story (PBS, Fridays, beginning Jan. 20, 9-9:30 p.m., check local listings for premiere and repeats) starts its new season with an in-depth study of what may be the major press crisis of the decade: the Reagan administration decision to ban the press from the Grenada invasion. It is examined in its true perspective - a potential harbinger of coming restrictions on press freedom.

In the course of checking out attitudes on all sides, the show takes on the aspect of a reunion of two Carters - President Jimmy and ex-State Department spokesman Hodding, who served in the Carter administration. Says Jimmy: ''The oppressive steps (within the Reagan administration) that are being attempted to control information are both unprecedented and unnecessary.'' In a portion of the interview which may not be included in the final version of the show the former President says: ''I was concerned during the Grenadian experience at how willing the American people were not to be informed and to lash out at the press. . . .''

''Inside Story,'' the only regularly scheduled self-examination of the press on the air today, doesn't hesitate to allow anti-press opinions to be fully aired - 81 percent of the people who responded to a Houston Star-Telegraph poll felt the press is arrogant, indifferent to suffering, morbid with a tendency to invade the individual's privacy.

Time magazine correspondent Bernard Deiterich? expresses his belief that the Reagan administration's real victory in Grenada was its victory over the press . . . and the truth. There were ''phantom enemies and phantom battles'' reported by the Army before the free press was allowed to cover the invasion.

Perhaps the most telling point is made by ye olde CBS anchor man Walter Cronkite, who points out that ''in a democracy, the people not only have the right to know but a responsibility to know.''

In pinpointing what appears to be a systematic tightening of controls over the news, ''Inside Story'' is performing a major public service. It reminds us that freedom of information is a fragile right which needs constant surveillance by all of us in order to survive. I feel a bit more secure knowing that Hodding Carter and ''Inside Story'' are there doing the monitoring job on television.