"Truth has won," Arvind Kejriwal tweeted after the High Court's decision, adding that the court had "given justice to the people of Delhi."
Here is a timeline of events of the AAP MLA disqualification case:
March 13, 2015: The Arvind Kejriwal government passes an order to appoint 21 MLAs as Parliamentary Secretaries.
June 19: The appointment was challenged by advocate Prashant Patel who sought their disqualification with then President Pranab Mukherjee.
June 24: Legislative Assembly passes the Delhi Member of Legislative Assembly (Removal of Disqualification) (Amendment Bill), 2015 excluding Parliamentary Secretaries from 'Office of Profit' with retrospective effect.
June 13, 2016: Then President Pranab Mukherjee refuses to give his assent to the bill.
June 25: 14 bills passed by the Delhi government, including the Bill on Parliamentary Secretaries, are returned by the centre.
July 14-21: Election Commission gives hearing to 21 AAP MLAs.
September 8, 2016: The Delhi High Court sets aside an order of the Kejriwal government appointing 21 of the party's MLAs as parliamentary secretaries.
September 8: Election Commission issues a show cause notice to 21 AAP MLAs.
January 6, 2017: Jarnail Singh, AAP MLA from Rajouri Garden, resigns.
August: The 20 AAP MLAs move Delhi High Court against the EC's June 24 order.
October 9: EC issues notice to AAP MLAs, seeks explanation.
January 19, 2018: Election Commission recommends to President Ram Nath Kovind the disqualification of the 20 AAP MLAs.
January 20: President Kovind approves the EC's recommendation of disqualifying the 20 AAP lawmakers.
January 24: MLAs moves High Court seeking quashing of the decision.
February 7: The HC fixes day-to-day hearing of the MLAs' pleas.
February 28: The High Court reserves order on AAP MLAs' pleas.
March 23: The High Court quashes notification that had led to the disqualification of 20 AAP MLAs.
With inputs from PTI