just a fact as well,
it is easy to point them out, at least, when they try to cancel a nice layover, even you are legal to do it.
they did it with me but only one time, because i followed it up, with all names.
went to rostering manager with all the evidence - got my layover back in 1 minute after i told him, i will take this a level higher.
since then, it never happened again, they just punish me now with not giving me my requests.
but am up to this already as well.
cheers