Sir Van Morrison is launching legal action against a ban on indoor gigs due to the coronavirus pandemic.
It comes after the star was accused of sending a "dangerous" message last year by writing three songs denouncing COVID-19 lockdowns, alleging scientists were making up "crooked facts" to justify restrictions to "enslave" the population.
How the COVID pandemic is affecting performers
Sir Van, 75, was able to perform in England in 2020, with a show at the London Palladium in September, as rules were different, allowing risk-assessed and socially distanced shows under the previous tier system.
Hospitality and entertainment venues are currently closed as part of a six-week lockdown in Northern Ireland – but even during periods of eased restrictions, live music has still not been allowed.
Solicitor Joe Rice, on behalf of Sir Van, said live music had not been defined in Northern Ireland's coronavirus regulations, with effectively a blanket ban imposed on everything from a heavy metal band to a harp soloist.
Mr Rice has issued pre-action correspondence to Stormont's Executive Office and the Department of Health, calling on ministers to make public the medical and scientific basis for regulations.
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He said Sir Van will argue the ban is unsustainable in law and is not based on credible scientific or medical evidence.
If it is not lifted, the star will seek leave from the High Court in Belfast to challenge the prohibition by way of judicial review, he added.
"Many people in the music and arts world in Northern Ireland have been devastated financially, socially and artistically by this complete ban," Mr Rice said.
"This differs from the law in England and Wales and the evidence behind such a negative decision in this jurisdiction is far from obvious.
"Sir Van is taking this action on behalf of the thousands of musicians, artists, venues and those involved in the live music industry.
"He has been supporting many artists throughout this pandemic and is determined to ensure that, as we endeavour to emerge safely from this lockdown, artists and musicians will have a proper opportunity to play their part through live music to restore the cultural, social and economic wellbeing and success of our society."