Who is responsible??

[H2Andy]

Perhaps some of our resident lawyers could tell us. Until then I suspect with government regulation of the airline industry, and high paid lawyers to draft the contracts of carriage, its pretty much a lock.

those restrictions are part of an enforceable contract, which you implicitly
agreed to abide by when you agreed to use the services provided. there's a long line of "common carrier" cases, dating back over two centuries, which would uphold the terms dictated by the airlines, so long as they are not against public policy or in violation of any laws to which the airlines are subject.

for example, an airline couldn't allow smoking in their airplanes by
putting in fine print "smoking will be allowed on this flight," since that
would violate existing law.