No there isn't a law but I suspect that a lot of recruitment agencies & companies in the private sector still take the view that working life in the public sector is less pressurised and more lenient about sick leave and fear that individuals might not be able to adapt to the profit culture which drives commercial enterprises. Also, sometimes the actual strategic issues involved in some of these functions may be slightly different in public and private sectors , i.e. if you're in HR and involved in compensation & benefits, you're likely to be working with different salary & reward systems, sales force car schemes, succession planning, etc. which don't necessarily function in the same way in the public sector. Also these days, I can't imagine many individuals in the public sector wanting to opt out of the local government pension scheme. It's a pretty cold world out in the private sector now when virtually all final salary indexed linked pension schemes have been abandoned because of their cost so working for the government does have its advantages.