It has power to legislate in a wide range of areas that are not explicitly reserved to the Parliament of the United Kingdom, and to appoint the Northern Ireland Executive.

The Assembly is one of two "mutually inter-dependent" institutions created under the 1998 Good Friday Agreement, the other being the North/South Ministerial Council with the Republic of Ireland.

To this end a new legislature, the Northern Ireland Assembly, was established in 1973 with a power-sharing Executive taking office in January 1974.

Unionist representatives refused to participate in the Good Friday Agreement's institutions alongside Sinn Féin until they were assured that the IRA had discontinued its activities, decommissioned its weapons, and disbanded.

The Assembly, already suspended, was dissolved on 28 April 2003 as scheduled, but the elections due the following month were postponed by the UK Government and were not held until November that year.

[8] Multi-party talks in October 2006 resulted in the St Andrews Agreement, wherein Sinn Féin committed to support the Police Service of Northern Ireland and the mechanism for nominating First and deputy First Ministers was changed.

In May 2006, Ian Paisley, leader of the DUP, had refused Sinn Féin's nomination to be First Minister alongside Sinn Féin's chief negotiator, Martin McGuinness, as deputy First Minister; after the St Andrews Agreement, these positions were now chosen by larger parties only, while the holders of other positions were elected by sitting MLAs.

The Transitional Assembly first met on 24 November 2006 but proceedings were suspended due to a bomb threat by loyalist paramilitary Michael Stone.

The DUP and Sinn Féin consolidated their positions as the two largest parties in the election and agreed to enter government together.

In the wake of the Renewable Heat Incentive scandal, McGuinness resigned from his post in January 2017, bringing an end to almost a decade of unbroken devolution.

Negotiations mediated by then Secretary of State James Brokenshire missed the three-week deadline provided in law for the formation of an Executive.

[21][22] Over time, further legislation was passed for Northern Ireland at Westminster, repeatedly extending the deadline for Executive formation although no direct rule ministers were appointed during this suspension.

[24][25][26] In February 2021, DUP MLAs threatened to bring down the Assembly and force an early election in protest at Boris Johnson's Brexit deal, which would put a border in the Irish Sea.

However, at both these meetings, the DUP refused to assent to the election of a speaker[31] as part of a protest against the Northern Ireland Protocol, which meant that the assembly could not continue other business, including the appointment of a new Executive.

[31] After the deadline set by Westminster for restoring devolved government was missed, the Northern Ireland secretary was legally required to schedule the election in the following 12 weeks.

[34][35] Further extension of the deadline to 8 February 2024 was brought about by legislation in the Westminster Parliament as a result of continued refusal by the DUP to form an executive.

[38] A sitting of the assembly was called for 3 February 2024 at which Edwin Poots was elected as Speaker and a new executive led by Michelle O'Neill and Emma Little-Pengelly was formed, restoring devolved government in Northern Ireland.

The BIIGC guarantees the Government of Ireland a say in areas of bilateral co-operation and on those matters not yet devolved to the Assembly or the North/South Ministerial Council.

It initially had 108 members (MLAs) elected from 18 six-member constituencies on the basis of universal adult suffrage and the single transferable vote.

[55][56] The Northern Ireland Act 1998 provides that, unless the Assembly is dissolved early, elections should occur once every four years on the first Thursday in May.

[citation needed] Which parties can appoint ministers to the Northern Ireland Executive is determined by a combination of mandatory coalition, the D'Hondt method and cross-community support, depending on the role, as explained above.

[59][60] A party may now form or join an Assembly Opposition, granting it additional speaking, scrutiny and funding rights, if it was entitled to Ministerial roles under the D'Hondt method and declined them, or if it wins 8% or more of the seats.

Even within the Executive, however, the parties (which have collectively held large majorities in the Assembly) have frequently voted against each other due to political and/or policy differences.

At the 2003 election, the DUP and Sinn Féin displaced the more moderate UUP and SDLP as the largest parties in the unionist and nationalist blocks.

The DUP, Sinn Féin, SDLP and UUP have remained the largest parties in the Assembly and so far the only ones entitled to ministerial roles in the Executive under the D'Hondt method.

The centrist Alliance party secured the roles of Speaker from 1998 to 2007 and Minister of Justice from 2010 to 2016 (and again from 11 January 2020) thanks to cross-community support, and has seen an increase in its seat wins from 6 to 8.

Independent unionist Claire Sugden gained the cross-community support needed to take over the Ministry of Justice.

[64] A 5th Executive was formed on 11 January 2020 following the 2017 election results, which saw the unionist block lose its Assembly majority for the first time.

[65] The usual four largest parties had won enough seats to win ministerial roles under D'Hondt (the DUP three, Sinn Féin two and the SDLP and UUP one each provided neither of them choose to enter opposition[66]).

Dáil Éireann, the lower house of the Oireachtas (Irish Parliament), uses the same single transferable vote system for elections as the Assembly but does allow by-elections to fill vacancies.