In the EU, many companies (esp. government) are required by law to layoff recent hires first, or in a particular order. Governments have largely decided that the government, not large companies themselves, do union negotiation, giving what the government wants, tempered a bit by negotiations (but NOT negotiated with the employees themselves), the force of law.
And mostly it's most-recent hire gets fired first. Of course the government does exempt itself from these regulation: both union folks themselves and people that are for various reasons placed by government (e.g. people who have a regulatory function, but work/are paid by the bank, and usually a whole management structure above them), cannot get fired. Only in healthcare have I really seen that there's a real order, and of course, it's based on perceived status. Maintenance personnel gets fired first, administrators last. Despite the obvious problems this generates for the care patients receive.
The real kick in the nuts of these agreements is that because they have force of law, they override your contract (instead of contracts taking precedence like in the private sector) and are not bound by many rules (e.g. they can devalue pensions already earned AFTER THE FACT. For example, say you "earn" 100 per month pension for every year of work. After 20 years, they suddenly decide that, no, they're only going to pay you 50. Despite you having already earned that)