Illegal construction without minimum distance to neighboring property

my brother-in-law had exactly the same situation after buying his house. Neighbors courted him accordingly to design a new building that violates the boundary distances.
Simply but firmly say, you don’t know what you will want to do with the property later, and therefore the fairest solution is the one provided by the state building code without any recognition of boundary distances to your detriment.....

That is exactly my fear, that in 5, 10, or 30 years my signature will be pulled out of the hat with the motto: "It didn’t bother you back then anyway..."
When I see what developers build on the smallest space, they surely use all means to squeeze out the biggest profit ops:

If you have worries and stomach aches, then just leave it. Say that you don’t want it and that’s that. Even if, for example, an employee at the authority provides assistance with wording, due to a lack of legal knowledge they cannot foresee all possible consequences.

Now listen to yourself: if you hadn’t had a problem with it from the start, you wouldn’t be here now. So you have a problem with it, but you want to "do something good" for the neighbor or you are simply reluctant to say no. You don’t want it, tell him. His problem, not yours.

And now listen to yourself: if you hadn't had a problem with it from the start, you wouldn't be here now. So you have a problem with it, but you want to "do something good" for the neighbor or you simply hesitate to say no. You don't want to, tell him. His problem, not yours.

I was actually clear that I would not sign it. I wanted to hear other opinions here in the forum because you often overlook something and can't see the forest for the trees. It has been very enlightening here so far and gives me many arguments that I will definitely need because the seller will not be satisfied with a “no.” But he will have to swallow that bitter pill.

So far it has been very insightful here and gives me many arguments that I will definitely need, because the seller will not be satisfied with a "no."

The other party seems to be putting a lot of pressure on you. I hope you stand firm. Do you have someone in your household who supports you in asserting your justified interests? Please do not let yourself be morally pressured either; setting boundaries is important for a good neighborly relationship. The other side would be the one to apologize and make amends, if anything at all.

The seller "should just" lower the purchase price for the house he sold.

Personally, I would try to achieve the dismantling in order to be on the safe side for the future and to prevent further discussions. If the new buyer needs the square meters of living space from the illegal construction at your expense, he will have to buy another, larger house.

Maybe many nonsensical things are in the state building regulations, which I cannot assess due to lack of expertise (but I will not assume it for now), but in my opinion, the rules on minimum boundary distances make sense.
(I don’t personally like that they can be circumvented with garden sheds and garages/carports, but the legislator must have had a reason for it.)

This approach seems to me the most reasonable ...

A common procedure is that a more or less short text is written on the construction plans, which is then signed, e.g.
I have taken note of the construction project. I agree with the reduced border distance of 2.30m, as long as this does not result in any building law consequences for my property.
Only what is stated in this declaration will be recognized by you. No further consequences can be derived from it, let alone entries in the land register.

... with one deviation: in the text proposal (italic) I would replace "the construction project" with "the approval application," since we are not talking about a new building here, but about the subsequent approval for the (future) legalization of the unauthorized building.
Or – if you see a relevant additional benefit from 70 cm more carport width – you follow the suggestion of .

I have thought about it again: In my opinion, the previous owner of the neighboring property/house owes you thanks, as you have "tolerated" his boundary violation, even if out of ignorance, and he may also have made money from it by being able to offer his tenants more living square meters or living value. (?)

I find it wrong to transfer this now to the next buyer of the property/house and then possibly to the buyer after that and the one after that, etc. You do not know what you will want to do with your own property one day, what disadvantages the reduced boundary distance might cause you, what neighbors you will have (I have the example from the thread in mind) even if the neighboring property/house is sold again, etc.

Therefore, I stick to the opinion that the sale of the neighboring property/house should be used to put everything in order now and act according to the law and regulations. That way you will be on the safe side. And if I try to put myself in the shoes of your new neighbors (and they are relevant, not the previous neighbor), I think they should understand that.