The employment relationship is governed by several layers of terms, only some of which are written down.
Express terms
What the written contract states.
Statutory rights
Legal minimums that override contrary contract terms.
Which is why some clauses are unenforceable.
Implied terms
Obligations read into every contract by law.
Which include mutual trust and confidence in many jurisdictions.
Changes to terms
Generally requiring agreement.
Which employers sometimes attempt unilaterally.
Why unenforceable clauses appear anyway
A contract cannot remove a statutory right, but it can be written as though it does, and many are.
Which means a clause stating something contrary to law is simply void rather than binding.
Employees frequently comply with terms that would not survive a challenge, because the contract says so and nobody told them otherwise.
Restrictive covenants
Post-employment limits on competing or soliciting.
Which are enforceable only so far as reasonable, and are frequently drafted more broadly.
Working time and pay
Statutory minimums on hours, rest and pay.
Which apply regardless of agreement.
Written statement requirements
Employers obliged to provide defined particulars.
A general note
Employment law varies enormously by jurisdiction; this is description rather than legal advice.
What to read before signing
Notice periods, probation terms, working hours, pay arrangements, holiday, and anything restricting what you may do afterwards.
Which are the terms that actually affect you.
Clauses restricting future employment deserve particular attention, because they are frequently accepted without thought and occasionally enforced.
Staff handbooks
Policies that may or may not be contractual.
Which the contract usually states.
Variation clauses
Employer rights to change terms.
Which are limited in most jurisdictions.
Getting advice
Employment advice services, unions and citizens' advice organisations.
Which are frequently free.
A general note
Employment law is jurisdiction-specific and this is general description rather than legal advice.
What matters most in practice
Notice periods, how pay and hours are defined, what happens during probation, and anything limiting what you can do after leaving.
Which are the terms that actually come up.
Most contractual disputes concern one of those four, and reading them carefully at the outset is the cheapest possible protection.
Contractor and employee status
Classification determining rights.
Which is decided by the reality of the arrangement rather than by the label.
Collective agreements
Union-negotiated terms applying to a workforce.
Which may sit above individual contracts.
Keeping records
Contracts, amendments and correspondence.
Which is what any later dispute turns on.
A general note
This is general description; employment law is jurisdiction-specific and advice services are usually free.
Why it is worth knowing how these things work
Most of the systems that shape ordinary life are invisible by design. Nobody explains why a parcel took an odd route, why a film left a streaming service, why a wait extended, or why a price changed between two searches.
The absence of explanation is rarely deliberate concealment. It is that the people running these systems are solving their own problems, and the reasoning behind their decisions is obvious to them and completely opaque from outside.
Understanding the mechanism does not always change what you can do about it. It does remove a category of low-grade frustration that comes from assuming something is arbitrary, unfair or aimed at you personally when it is usually none of those things.
The pattern that recurs
Across almost all of these systems, the same three things turn out to be true. The behaviour that looks irrational from outside is optimising for something the observer cannot see. The cost that seems unexplained is usually concentrated in one specific stage of the process. And the information that would resolve the confusion is generally published somewhere and read by nobody.
That last point is the most useful. Regulators, operators and industry bodies publish an enormous amount of explanatory material that answers exactly the questions people complain about not being able to get answers to. It is dry, it is not promoted, and it is free.
A note on sources
Where regulation is involved, national regulators publish the actual rules and they are generally clearer than press coverage of them. Where an industry is involved, trade publications aimed at people working in it are considerably more informative than consumer coverage.
Practices described here vary substantially between countries, and anything with legal, financial or medical consequences warrants checking against the rules that apply where you are.
The pattern that recurs
Across almost all of these systems, the same three things turn out to be true. The behaviour that looks irrational from outside is optimising for something the observer cannot see. The cost that seems unexplained is usually concentrated in one specific stage of the process. And the information that would resolve the confusion is generally published somewhere and read by nobody.
That last point is the most useful. Regulators, operators and industry bodies publish an enormous amount of explanatory material that answers exactly the questions people complain about not being able to get answers to. It is dry, it is not promoted, and it is free.