Am I entitled to take an ownership deed for the apartment that I fully built with my own money in my in-laws' house, without them sharing in the ownership of the land?

The questioner did not clarify what was agreed upon between him and his wife's family regarding the construction. However, it appears from the question that the wife's family permitted him to build without compensation, and therefore, he owns what he built and has the right to a deed proving that. Furthermore, the imminent issuance of a law prohibiting additional stories does not negate the right of the owner of the additional story, as he could have built it before the law was issued.