By itself, nothing, since they still broke the law when they committed their initial offense and were duly convicted of it. In principle, you could even prosecute and convict somebody after the legalization for an act committed before, though it seems unlikely any prosecutor would bother. Though if you bothered to legalize something, you might also want to commute the sentences of anyone previously convicted.

This is a mirror of "Ex Post Facto" - if you pass a law making some act illegal, you can't convict somebody who did that act before the law was passed because it wasn't illegal at the time. In principle, it's supposed to be possible for an individual to determine if an act they are considering performing is illegal or not, and for them to be able to rely on that determination.

To be slightly annoyingly pedantic, the actual return trajectory is most likely nowhere near the ISS, but if they were planning to dock with the ISS, they would presumably cheaply adjust their incoming trajectory to be as close to the ISS orbit as possible while still far away. If they were rather good at it, presumably they could get pretty close to only that 4km/s of total DeltaV to match orbits.

Of course that's still a hell of a lot of DeltaV versus aerobraking.

The gear itself doesn't wear at all from static force, since it's just pieces of metal meshing with each other but not moving. They can wear a bit from turning under power, though this is pretty negligible in vehicle transmissions that are working properly.

I think you're thinking of clutches. Manual transmission cars use clutches which physically slip to start from a stop. If you left one partially engaged while braked at a full stop, it would indeed wear very fast, so don't do that. Automatic transmission cars use torque converters, which as described in the other posts is a fluid coupling instead of a mechanical slippage, so it doesn't wear significantly from exerting force while the car is held at a stop by the brakes.