This is the third constitution1) of the pan-human polity now known formally as 'The Solar Republic' and more often colloquially refered to as simply 'Earth' or the 'Earth Empire'. In its unamended form this is the constitution that was adopted in 2947 following the Great Reform Act. This version has stayed extant because it is more easily amended than previous versions and also, many believe, because the turbulence of colonisation and political change has settled somewhat with the existence of many other polities.
There was a move to re-constitute in the mid to late 31st Century to take a stronger republican slant but after the secession of the Republic of New Venus most of those calling for the stricter central rule left to settle in the RNV. This ensured that the existing constitution remained in place.
Since the constitution's formal adoption there have been many amendments, the most recent being the clarification of the maximum permissible length of a First Minister's appointment.
note: the introduction is not part of the constitution document, it starts with the 'Preamble'
We, the People and Senate of Earth, do adopt this constitution of the Solar Republic to ordain a more settled form of government for humanity, better mutual defence, justice, freedom from oppression and economic prosperity for all of humanity both now and in the future.