A B737-300 CAPT QUESTIONS THE DEFERRAL PROCS USED WHEN A FUEL QUANTITY INDICATOR AND AN AIRSPD INDICATOR ARE DEFERRED PER THE MEL.

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ACFT X RECEIVED INBOUND WITH 2 DEFERRED ITEMS. ITEM #1 WAS FOR L-HAND FUEL QUANTITY INDICATOR INOP AND ITEM #2 WAS THE CAPT'S AIRSPD INDICATOR INOP. THE MEL CARD FOR FUEL QUANTITY INOP RESTRICTS THE USE OF FMC GENERATED SPDS AND WTS. THE MEL CARD FOR AIRSPD INDICATOR REQUIRES THAT THE EADI SPD TAPE FOR THE AFFECTED SIDE 'MUST OPERATE NORMALLY.' DUE TO THE INOP FUEL QUANTITY; CERTAIN FEATURES OF THE FMC AND VNAV ARE INHIBITED. IT IS NOT POSSIBLE TO DISPLAY CERTAIN INFO ON THE EADI SPD TAPE (VREF; VFE; HIGH SPD BUFFET AND MINIMUM MANEUVERING SPD). THE AIRSPD FUNCTION; VNE AND MCP COMMANDED AIRSPDS ARE DISPLAYED. THE SPD TAPE SHOWS EXACTLY THE SAME INFO AS THE AIRSPD INDICATOR. I FELT THIS SATISFIED THE 'MUST OPERATE NORMALLY' REQUIREMENT SET FORTH IN THE MEL. THE ACFT HAD FLOWN INTO ZZZ WITH THESE ITEMS DEFERRED AND THE MRD AND RELEASE CHK WAS ACCOMPLISHED WITHIN 10 MINS OF DEP AND SHOWED THAT THE MAINT RELEASE WAS CURRENT. WE PUSHED BACK AND TAXIED OUT WITH INTENT TO FLY. DURING TAXI OUT; GND CTL ADVISED US TO CONTACT THE COMPANY. WE WERE TOLD TO RETURN TO THE GATE AS REQUESTED BY MAINT. WE DID. AFTER OUR RETURN TO THE GATE; I CONTACTED MAINT CTLR FOR ADDITIONAL INFO. THE MAINT CTLR HAD MADE A DETERMINATION THAT THE LACK OF FMC INPUTS DID NOT MEET THE REQUIREMENTS OF THE MEL FOR THE FUEL QUANTITY INDICATOR BECAUSE THE FMC COULD NOT GENERATE SPD INFO FOR THE EADI SPD TAPE. HE TOLD ME THAT THEY HAD DEBATED IT IN DEPTH AND ALSO INFORMED ME THAT A PREVIOUS CAPT IN ZZZ1 HAD REFUSED THE ACFT FOR THAT VERY REASON (NO MENTION IN THE PAPERWORK AS AN 'EG' NOTE). THE ACFT WAS FLOWN BY ANOTHER CREW FROM ZZZ1 TO ZZZ WITH THE DEFERRALS. DISCUSSION WITH THE AMT REVEALED THAT THE ACFT WAS ORIGINALLY ON A 'MUST FIX' STATUS INBOUND TO ZZZ. THE AIRSPD INDICATOR WAS REPLACED AND WE OPERATED WITHOUT FURTHER INCIDENT. 2 ISSUES CONCERN ME: 1) HOW COULD AN ACFT GET OFF THE GATE AND SHOW A CURRENT MRD WITH A MUST FIX ITEM? AND 2) ON THE MEL CARD FOR AIRSPD INDICATOR INOP; THE TERM 'MUST OPERATE NORMALLY' IS VAGUE AND NEEDS CLARIFICATION. WHAT IS THE LEGAL STANDARD OF 'MUST OPERATE NORMALLY?'