[6] Sam Rainsy went into exile on February 3, 2005, citing fear of arrest after a vote in the National Assembly removed parliamentary immunity from himself and fellow SRP MPs Chea Poch and Cheam Channy.

[7] Rainsy faced multiple criminal defamation charges after accusing the Cambodian People's Party and Funcinpec of corruption in the formation of the current coalition government.

On 12 July 2013, King Norodom Sihamoni granted a royal pardon to Rainsy at the request of the Prime Minister, Hun Sen, allowing the opposition leader to return to Cambodia without threat of imprisonment, although he remained ineligible for candidacy in the 2013 general election.

[14] The CNRP gained 55 seats in the National Assembly although Sam Rainsy and Kem Sokha have denied these results and accused the ruling party of poll fraud.

[17] In 2016, Rainsy again left Cambodia after being charged with defamation and incitement for accusing Hun Sen's government of orchestrating the high-profile murder of political activist Kem Ley.

In 2019, Rainsy announced he would return to Cambodia on Independence Day, but was blocked following the Cambodian government's intervention with airlines and with Thailand, where he would have transited.

In April 2008, Rainsy accused Cambodia's then foreign minister Hor Namhong of having served under the Khmer Rouge[25] as director of the Beoung Trabek prison, where torture and murder was carried out.

The CNRP was also given leadership roles in parliament, with Kem Sokha as the first vice president of the National Assembly and other politicians chairing 5 of the 10 parliamentary commissions.

On 1 December 2015, the Phnom Penh Municipal Court summoned Sam Rainsy in absentia to clarify a statement he posted to his Facebook account following a defamation complaint by parliamentary president Heng Samrin.

[33] Less than two weeks earlier, the same court had issued another summons for Sam Rainsy to appear for questioning over his alleged involvement in using a fake map to resolve a border dispute with Vietnam.

Sam Rainsy responded by creating the Cambodia National Rescue Movement (CNRM), which seeks to increase international pressure on the Hun Sen regime.

The US said in February 2018 that it was suspending or curtailing programs[37] that support the Cambodian military, local government authorities and a major taxation body.

In March 2018, Kem Sokha's period of detention without trial was extended for six months,[40] meaning that he will be in prison when the country's national parliamentary elections scheduled for July 2018 takes place.

[23] Rainsy was denied boarding on a Thai Airways flight from Paris to Bangkok,[21] from where he planned to travel to Cambodia, on 7 November, despite having a valid ticket.

During the COVID-19 pandemic, Sam Rainsy advocated the introduction of immunity passports based on tests for antibodies as a way to restart the international economy.