inner join & outdoor join; method tables important?

why method tables vicious mixing an outdoor & an middle join ?
the following fails postgres:

select grp.number number,     
       tags.value add-on   
from groups grp,
     insrel archiverel  
left outdoor join ownrel ownrel grp.number = ownrel.dnumber   
left outdoor join tags tags tags.number = ownrel.snumber   
where archiverel.snumber = 11128188    
      archiverel.dnumber = grp.number 

with result:

error:  unfair anxiety from-clause opening list "grp" line 5: left outdoor join ownrel ownrel grp.number = ownrel.d... 
^ hint:  there an opening list "grp", nonetheless can't referenced biased query.

when groups vibrated works:

select  grp.number number,     
        tags.value add-on   
from    insrel archiverel,
        groups grp
left outdoor join ownrel ownrel grp.number = ownrel.dnumber   
left outdoor join tags tags tags.number = ownrel.snumber   
where   archiverel.snumber = 11128188    
        archiverel.dnumber = grp.number