I don't see how that is enforceable except in circumstances where the creative content of your work is in some way related to what the company is involved in (which can be expensive for a large for a multinational corp., admittedly)

For example, the photographs of your family taken by yourself. Would you expect your employer to retain copyright?

They have a legal department and you don’t though right, so if they chose to fight it you’ll probably decide it’s not worth it.

As I said, mine too, that does not mean it is in any way legal (and as most of my coworkers have FOSS projects of their own, I would like to see them try).

I believe the use of a contract and signatures in fact does literally make it legal, since that is the point of a contract. Everything depends on what you signed.

A contract cannot override law. A prime example is the minimum wage laws - it is illegal for an employer to pay less than the minimum wage, and an employee can't sign a contract to make it actually alright after all.

There are laws, and there are judgements which are the courts interpretation of the laws; a signed contract does not have the power to overturn either.

It is the job of HR & Legal depts to make sure a contract is legally viable, not mine, and I happen to know my rights. There are at least 5 illegal clauses in my contract, and I am certainly keeping them close by if I need to go to court against them one day.

You could sign yourself into slavery, that doesn't make it legal.