With understandable but misguided concern, The Post's editorial June 16 assures readers that the dismissal of charges against Cpl. Arnold Bracy can have only two possible explanations. "Either the original charges were blown out of proportion and no serious offenses occurred or a serious case was mishandled by investigators and now a prosecution is impossible."

But what about a third alternative -- that is, that these are difficult cases? Consider the following:

The alleged offenses were committed in an unfriendly foreign country. Such a location obviously limits our access to willing and available witnesses, and, just as important, no paper trail -- for example, airplane tickets and hotel reservations -- exists to document acts allegedly committed in connection with the charged offenses.

The investigation has been conducted from nearly the beginning under congressional and media spotlights. Officials pressed for comments and reactions have done so with less than complete information. Internal memos concerning fast-breaking events have been leaked before those to whom they have been addressed can act on them.

Other interests, such as the need for damage assessments and continued security, have competed with investigative and prosecutorial priorities. Of necessity, therefore, the investigation and prosecution of these cases have involved nearly every department and agency of the federal government responsible for foreign affairs, national security and law enforcement. Coordinating and accommodating all these players is a large order.

The strict requirement of the Uniform Code of Military Justice that cases be brought to trial in 90 days or less means that tough tactical decisions must be made lest a strong case, methodically developed, is lost irrevocably for lack of speedy trial. The dismissal of charges against Cpl. Bracy does not bar their resurrection should the continuing investigation produce additional evidence.

Finally, under the code, confessions must be corroborated before they may be admitted into evidence. In other words, their essential elements first must be established by independent evidence, and an accused's admissions to a third or fourth party do not constitute such evidence.

Overlooking this possible alternative explanation, the editorial offers three events to support its proposition that the "story began to unravel" and the charges are "trickling away." First, the "most serious charges against Sgt. Lonetree have been dropped." Indeed, those based on Cpl. Bracy's confession, which implicated Sgt. Clayton Lonetree and which was later recanted by him, have been. Cpl. Bracy's confession, even if admissible in all respects against him, could not be used against Sgt. Lonetree; only Cpl. Bracy's in-court sworn testimony is. Absent other evidence, the convening authority had to drop those charges based on Cpl. Bracy's confession. I note, however, that the charges remaining carry a maximum life sentence. That seems serious to me.

Second, Sgt. John Weirick "was never charged and has been released." True again, but left out is the fact that he admitted to offenses allegedly committed in 1982, several years beyond the applicable statute of limitations of two years. Incidentally, the statute under federal criminal law is five years.

And finally, we have the Bracy case itself, in which the same evidence -- or lack of it -- caused the dropping of some of the charges against Sgt. Lonetree.

While the editorial thus analyzed hardly presents overwhelming evidence of a "Moscow Marine Muddle" or "terrible bungle," the list of questions with which it ends certainly are deserving of answers. Inevitably they will come, but only as a result of a "slow sorting out" which the editorial decries. M. E. RICH Deputy Director, Judge Advocate Division Marine Corps Headquarters Washington See today's editorial.