a lock on luggage

Are the locks not TSA approved? If they are, you don't have to do anything. If not, you either have to take it off the checked bag or risk them cutting it off if they want to peek inside. The carry one doesn't matter, you can unlock it at anytime if TSA wants to peek inside.

TSA can clip your lock without permission and outside your vision. I've later found a notification inside my checked luggage although I don't use a lock anyhow. Why bother?

I never lock my luggage. I do run a cable tie through the two zipper pulls to fasten them together - this more to make sure the suitcase doesn't gap open for any reason and it makes for a minor deterrent to theft. On trains we cable tie our two bags together - much harder to make off with. I carry a pair of children's safety scissors in my travel day bag - you know, the kind with the rounded tips. They come in handy for opening grocery store items etc., weigh almost nothing and cuts those cable ties in a snap. Also useful for cutting out bits and pieces of things for my scrap book. Allowed in carry on by TSA.

Are you asking about security on the return trip? That is, do other countries require locks that can be opened by security on checked bags?

I use cable ties, too. If they cut it off, they will replace it with a new one.