Health insurance, and Jedi-ism

One-and-a-half cheers for the vote on health reforms in the USA.

... and a segue from concerns about reproductive rights to ...

... a strange collision of worlds, where I'm talking to UK Civil Servants about what belief systems UK Equality laws are 'intended to protect' and discovering: certainly not Jedi-ism (because UK residents will generally consider it a trivial fiction), nor Marxism (because political beliefs are not covered) nor Darwinism (because scientific beliefs are not covered)

( Protected beliefs, prohibited conduct )

ETA You can currently respond to an EHRC consultation on their draft guidance relating to the Equality Bill 2010: http://www.equalityhumanrights.com/legislative-framework/equality-bill/

Equality from first principles?

So ... how about axioms-based equality laws? Where should the lines lay in law for illegal discrimiation?

For example, if the core tasks of a job require the employee to do X, and a candidate for that job cannot currently do X, nor reasonably be expected to be able to do X even with realistic training, technological support etc., then it would presumably be justifiable not to consider them further for employment.

Where can we draw legal lines from first principles?

What would be your fundamental determining principles for when differential treatment is justified?