This certainly the case in Europe anything over a certain overhang Front or Rear requires markers and if over 3m requires notification of movement.

Trailers over a certain length also have to have side markers as well as reflective boards.... in extreme cases a reflective board with LONG VEHICLE on if the combined length requires it.

Then weights require brakes etc

Number of axles with brakes can affect the legal speed you can tow at in uk single axle non braked trailer 60mph braked twin axle 70mph

Complicated this towing lark ain't it!!!!!