[3] As part of his role in the pro-independence demonstrations prior to the Catalan independence referendum of 2017, he was imprisoned from October 2017 until June 2021 under charge of sedition brought by the Spanish prosecutor's office.

As a teenager, he studied mechanics in the vocational education centre Institut Escola Industrial i d'Arts i Oficis in Sabadell.

[16][17][18] This sedition was allegedly committed when they organized a protest on 20 September 2017 during Operation Anubis police raids to dismantle the framework of the 1 October Catalan independence referendum performed by the Spanish Civil Guard.

[19][20][21][22] They were accused of leading the protest of tens of thousands of people in front of the Catalan economy department heeding a call made by Òmnium Cultural and ANC.

[16] The investigating judge stated that the leaders did not call for "peaceful demonstration but to the protection of Catalan officials through 'massive citizens' mobilisations", which physically blocked the Guardia Civil from leaving the building for the entire day.

[33][34][35] But footage from that night also show Cuixart and Sànchez calling off the protests on top of the car at 11pm: "We are asking you, to the extent possible and in a peaceful way, to dissolve today's gathering".

[58] Amnesty International issued an official statement considering the charge of sedition and the preventive imprisonment "excessive" and called for their immediate release.

[59][60] Amnesty International calls on Spanish authorities to drop the charges of sedition and to put an immediate end to their pre-trial detention.On 7 March 2018 the Office of the United Nations High Commissioner for Human Rights reminded Spanish authorities that "pre-trial detention should be considered a measure of last resort" referring to Catalan politicians and activists arrested after the independence referendum.

[61] On 8 August 2018, PEN International made another statement asking Spanish authorities to release Cuixart and Sànchez and considered their detentions to be "an excessive and disproportionate restriction on their right to freedom of expression and peaceful assembly".

[62][63] Also, public figures such as Jody Williams, Noam Chomsky, Pep Guardiola, Angela Davis and Ben Emmerson demanded his freedom.

[64] The World Organisation Against Torture sent an open letter to the President of the Government of Spain Pedro Sánchez as well as the Spanish Attorney General and Spanish Ombudsman on 22 November 2018 demanding the end of the "arbitrary pre-trial detention and judicial harassment of Jordi Cuixart and Jordi Sànchez" and concluded "OMCT considers that the charges against them are unfounded and must therefore be dropped".

[69] On the same day, the European Democratic Lawyers association requested the immediate release of the Catalan leaders and expressed their concern because of the "lack of procedural guarantees during the trial".

[73] The OMCT also condemned the "disproportionate conviction of Catalan leaders",[74] as did world politicians such as Nicola Sturgeon, Yanis Varoufakis, the EFA and the EELV.

[75] Other international organizations also criticized the harsh sentence, such as Front Line Defenders, Liberties,[76] ELDH - European Lawyers for Democracy and Human Rights,[77] and AED (Avocats Européens Démocrates).

[82] In January 2021, 50 human rights defenders such as Yoko Ono, Irvin Welsh or Dilma Rousseff, and Nobel Prize winners such as Shirin Ebadi, Adolfo Pérez Esquivel, Jody Williams, Mairead Corrigan or Elfriede Jelinek, joined the Dialogue for Catalonia manifesto, calling for a dialogue between Catalonia and Spain to end the repression and advance towards a political solution.