AN AIRBUS A320 FLIGHT CREW REALIZES LATER THE ACFT THEY HAD FLOWN MAY HAVE BEEN RELEASED WITH A MAINT DEFERRAL THAT WAS NOT LEGAL.

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POTENTIAL ILLEGAL MAINT RELEASE. ACFT HAD CLASS II MAINT MESSAGE DEFERRED CONCERNING FLT CTLS. INBOUND ACFT HAD THE ADR 2 FAIL ON TKOF ROLL IN ZZZ AND AFTER CONTACT WITH MAINT CTL CONTINUED INBOUND TO ZZZ1. MAINT CTL CONTACTED CONTRACT MAINT AT ZZZ1 TO TROUBLESHOOT AND RELEASE AIRPLANE. CONTRACT MAINT SEEMED VERY UNFAMILIAR AND UNCOMFORTABLE WITH WHAT HE WAS DOING. WAS COACHED THROUGH THE BULK (IF NOT ENTIRE) PROCESS VIA CELL PHONE. THE ADR WAS NOT REPAIRABLE AND MAINT CTL DEFERRED THE UNIT AND ISSUED A MAINT RELEASE. THE DEFERRAL REQUIRED ALL FLT CTLS TO OPERATE 'NORMAL' AND INCLUDED A LIST OF FLT SYS THAT SPECIFICALLY HAD TO BE 'NORMAL.' MY CHK PLT CAPT NOTED THAT 1 ITEM LISTED ON THE DEFERRAL WAS 1 LETTER DIFFERENT THAN A CLASS II MAINT MESSAGE (SFCC VERSUS SFCS). THE FLEET HAS HAMMERED HOME THAT CLASS II MAINT MESSAGES ARE ADVISORY ONLY. THEY ARE GENERALLY REDUNDANT SYS AND THE MESSAGE IS JUST AN INDICATOR THAT THE SYS NEEDS ATTN. FLT PROGRESS NORMALLY TO ZZZ. AT THE ARR GATE THERE WERE MULTIPLE MECHS TO LOOK OVER THE DEFERRED SYS. THE PLTS SCHEDULED TO TAKE THE PLANE INDICATED TO US THAT IT APPEARED THIS PLANE WAS NOT LEGAL TO FLY. APPARENTLY A DIFFERENT MAINT CTLR WAS ON DUTY AND HE FELT THE SYS WERE IN CONFLICT AND THE PLANE WAS REMOVED FROM SVC. IT APPEARS I WAS CONVINCED TO OPERATE A PLANE THAT WAS NOT LEGAL TO FLY. IF SO; THEN COMPANY JEOPARDIZED THE SAFETY OF MYSELF; MY CREW AND 160 PAX. MAINTAINING AN ACFT CANNOT BE SUBJECT TO NEGOTIATION AND OPINIONS OF WHAT 'MIGHT' BE OK. PLTS DO NOT HAVE THE DETAILED RESOURCES AVAILABLE TO US TO DETERMINE THE INNER WORKINGS OF THE ACFT SYS AND POTENTIAL CONFLICTS. WHEN WE DEPARTED ZZZ1; I THOUGHT WE HAD COMPLIED WITH THE MAINT RELEASE. AFTER ARR AND THE FLURRY OF ACTIVITY I BECAME VERY CONCERNED THAT WE HAD 'BEEN HAD.' I CALLED MAINT CTL 4 HRS LATER TO ASK WHAT THE OUTCOME WAS AND DISCOVERED THE ACFT HAD BEEN OTS SINCE WE PARKED IT. MAINT CTL INDICATED IT WAS OVER A 'DIFFERENCE OF OPINIONS.' THAT IS NOT ACCEPTABLE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED WITH THE PREVIOUS FLIGHT CONTROLS CLASS 2 SYSTEM FAULT; THE #2 ADR (AIR DATA REFERENCE) FAULT AND THEN AN SFCS (SLAT/FLAP CONTROL SYSTEM) FAULT; ALL THIS DEFERRED AND BEING TOLD BY COMPANY MAINT CONTROL THEY WERE LEGAL AND THE FAULT MESSAGES WERE ONLY 'ADVISORY;' ONLY TO FIND OUT LATER THE ACFT WAS TAKEN OUT OF SERVICE WAS NOT ACCEPTABLE AND AN UNSAFE AND INADEQUATE MAINT APPROACH TO SAFETY.