try (ПРИМЕЧАНИЕ: работает не только для хранимых процедур):
SELECT
dp.NAME AS principal_name
,dp.type_desc AS principal_type_desc
,o.NAME AS object_name
,o.type_desc
,p.permission_name
,p.state_desc AS permission_state_desc
FROM sys.all_objects o
INNER JOIN sys.database_permissions p ON o.OBJECT_ID=p.major_id
LEFT OUTER JOIN sys.database_principals dp ON p.grantee_principal_id = dp.principal_id
WHERE o.NAME = 'YourProcedureName'