IT TOOK SOME extraordinary doing in Annapolis this year to win general agreement on a forward-thinking policy for Maryland prisons, but now comes the hard part; how do you release 451 inmates who are considered non-violent but whose chances of being rearrested may be greater than average? The answer lies somewhere between Gov. Harry Hughes and Parole Commission Chairman Henry P. Turner, who have been doing an Alphonse/Gaston routine at the prison doors.

Until the other day, each had seemed to believe in the idea of these releases; but without proper parole preperations for the inmates, neither the governor nor Mr. Turner has been eager to assume sole responsibility for such a move -- even in the face of a court-ordered June 1 deadline for eliminating overcrowding. They are both right -- for a hasty mass release of that many inmates would be reckless. Besides risking additional crime, any unusually high rearrest rate would be political ammunition for opponents of the governor's so-far impressive efforts to improve corrections policies.

The object should be to release non-dangerous prisoners -- but only if parole standards can be maintained. That means more money and people to cover the increased work involved. Additional parole and probation agents are essential before any large numbers of inmates are let out -- both for society's sake and for the welfare of the prisoners involved. The Cost of a sound parloe policy are not great compared with the costs of building more huge prisons and, in fact, may yield a greater return on the public's investment.