the un won't enforce it, it's proven it. the french won't enforce it.
the only way to enforce it is for israel to occupy the region south of the litani and will hezbollah agree to that?
what israel appear to be trying to do is actually push hezbollah north of the awaali river, which is north of not just the ancient hebrew-canaanite city of tyre but also the ancient hebrew-canaanite city of sidon. it's not clear if they intend to occupy up to the litani and demand demilitarization between the litani and awaali or actually push all the way to the awaali, but how can you blame them for pushing beyond the previous un resolution when the previous un resolution was not enforced?
should they ask for another un resolution that won't be enforced?
whether what they do is supportable in the end will depend on the precise actions but i actually have a hard time criticizing israel for annexing any region that is historically considered to be phoenecia because while the arguments are obtuse and arcane and awkward, they're also basically correct. the phoenecians were basically jews, which is why the romans treated the jews so poorly, which has set off centuries of persecution.
i just wish they'd try to assimilate the palestinians back into israel rather than try to get rid of them. they're closer to the ancient hebrews than anybody else.