The periodical has 'rigid' [='strict', 'inflexible'] guidelines for submissions.
a 'rigid' [='strict, unwavering'] adherence to the rules
The soldiers stood 'rigidly' at attention.
(..) I say "guilt," gentlemen... because it was guilt... that motivated her. She's committed no crime. She has merely broken a rigid and time-honoured... code of our society. A code so severe that whoever breaks it is hounded from our midst... as unfit to live with. She must destroy the evidence... (..)1962 To Kill a Mockingbird