FLT CREW MISINTERPRET CLRNC 'DSND AND MAINTAIN 17000 FT; CLRED FOR VUCAN STAR' AT CYYC TO ALLOW DSCNT TO THIRD INTXN AT OR BELOW 12000 FT. AS THEY DEPART 17000 FT ARTCC ALERTS THEM TO MAINTAIN 17000 FT AS ASSIGNED DUE TO TFC AT 16000 FT.

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WE WERE FLYING FROM MSP TO CYYC. AT ABOUT 60 MI FROM CYYC; EDMONTON CTR TOLD US TO DSND AND MAINTAIN 17000 FT AND WE WERE CLRED FOR THE VUCAN 7 ARR INTO CYYC. WE WERE AT 31000 FT. WE STARTED OUR DSCNT. THE VUCAN 7 ARR HAS A XING RESTR TO CROSS 'THIRD' (INTXN) AT 12000 FT. IT DOES NOT SAY EXPECT TO CROSS; IT IS A PUBLISHED XING RESTR. I HAVE FLOWN THIS ARR BEFORE AND IN THE PAST HAVE CONTINUED THE DSCNT TO MAKE THIS XING RESTR ONCE WE WERE 'CLRED' FOR THE ARR. IN FACT THE FIRST FEW TIMES I FLEW THIS ARR I QUERIED ATC IF THEY WANTED US TO CROSS 'THIRD' AT 12000 FT AND ATC CAME BACK WITH YES YOU HAVE BEEN CLRED FOR THE ARR. THIS TIME AS WE WERE PASSING THROUGH 17000 FT I INFORMED ATC WE WERE CONTINUING DOWN TO 12000 FT. ATC CALLED BACK AND SAID TO MAINTAIN 17000 FT. WE IMMEDIATELY ARRESTED OUR DSCNT BUT WENT ABOUT 500-600 FT BELOW 17000 FT. WE THEN IMMEDIATELY CLBED BACK UP TO 17000 FT. ATC TOLD US WE WERE SUPPOSED TO MAINTAIN 17000 FT. I TOLD THEM WE HAD BEEN CLRED FOR THE ARR. THEY DIDN'T CONTRADICT THIS BUT SAID WE WERE SUPPOSED TO MAINTAIN 17000 FT. IT SEEMS TO ME THAT WE WERE GIVEN A CONTRADICTORY CLRNC. IF WE WERE CLRED FOR THE ARR THEN WE WERE CLRED TO MAKE THE XING RESTR. IN THE FUTURE WE WILL CLARIFY WHAT WE SHOULD DO BUT I ALSO FEEL THAT THE ARR PLATE SHOULD SAY 'EXPECT TO CROSS' OR THE CTLR SHOULD NOT CLR YOU FOR THE ARR TILL THEY WANT YOU TO MAKE THE RESTR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR ADVISED HE SPOKE WITH THE CHIEF PLT OF HIS ACR SUBSEQUENT TO THIS EVENT AND CAME AWAY WITH NO CLRER PICTURE OF WHAT IS REQUIRED FOR STAR OPS IN CANADA. HE STATED HE FELT THE ONLY CERTAIN COURSE OF ACTION TO INSURE COMPLIANCE WITH ATC EXPECTATIONS IS TO INQUIRE SPECIFICALLY WHEN GIVEN A CLRNC FOR A STAR.