The passing of the referendum on full law-making powers was a pivotal point in the Assembly's history.
It heralded a new legislative system of direct primary law-making powers not seen in Wales since the days of Hywel Dda in the tenth century.
From the beginning of the fourth Assembly, permission from Westminster to legislate on devolved issues is no longer needed.
On 3 March 2011, voters in Wales decided by 63.5% to 36.5% to bring an end to the old system of legislating.
The referendum was enshrined in the Government of Wales Act 2006 and gives the Assembly similar legislative powers to Scotland and Northern Ireland.
A key commitment of the Labour-Plaid coalition government at the time, it was triggered unanimously by Assembly Members in February 2010.
The passing of the Government of Wales Act 2006 marked a significant increase in the Assembly's powers as it inherited the powers and budget of the Secretary of State for Wales, as well as most of the functions of the Welsh Office.
Tourism is one of the areas the Assembly legislates on
The act separated the Assembly's legislative and executive branches; a split that didn't exist before.
Put simply, the Welsh Assembly Government is responsible for the day-to-day running of the country, whilst the National Assembly for Wales, which consists of 60 members, scrutinises and debates the government's work.
When power was first devolved to Wales in 1999, the Assembly could only pass secondary legislation in certain devolved areas.
However, it crucially had no powers to bring about primary legislation. In other words - it couldn't make its own Welsh laws.
A change came about in 2006 following another Government of Wales Act, giving the Assembly the power to make its own laws.
Agriculture, fisheries, forestry and rural development
Ancient monuments and historic buildings
Education and training
Fire and rescue services and promotion of fire safety
Health and health services
Highways and transport
National Assembly for Wales
Sport and recreation
Town and country planning
Water and flood defence
Within these fields, there were defined policy areas that the Assembly could legislate on.
However, further powers could be devolved on a case-by-case basis, but only with the permission of both Houses of Parliament.
referendum on full law-making powers
put an end to that system.
The Assembly can now pass Acts of the Assembly on devolved areas without requiring prior consent.
There are still a number of policy areas that are completely controlled by the British government, including constitutional affairs, defence, and foreign affairs.
So for example the Assembly government isn't able to create a bank holiday on St David's Day or legalise fox-hunting, even if it wanted to.
However the government in Cardiff Bay has adopted a series of measures designed to put "clear red water" - to quote the former First Minister Rhodri Morgan - between Wales and Westminster.
Some, such as
to museums and galleries, were later copied in England.
Others, such as
free bus travel
for pensioners and the abolition of
, remain Welsh.