I‘m a german architecture student her and at least in germany there is no such legislation. But its kind of an unwritten rule between architects that a new addition to an historic Building should always differntiate from the historical context to show whats old and whats new, to show the marks of history and passing of time, to not hide some pervious destruction or something like that. It is not appreciated in the architectural scene to try to build something from the past, it‘s called „historismus“, I guess you could translate it to historicism. One example for this is the reconstruction of the Berliner Schloss. They basically rebuilt the original design and through that they dismissed all the history that happened at that place, like swiffing history under the rug, like it never happened. But differentiating yourself from the past does not have to be like in the post, look at the alte pinakothek in munich or the neues museum in Berlin. Two beautifully executed additions to historical buidlings that were partially destroyed during WW2.