British military men and women planning to join a rally in support of a Royal Marine jailed for murdering an Afghan insurgent have been banned from attending "political protests".
More than 1,300 people are expected to gather at Parliament Square in London from noon on Wednesday in a public show of support for Sgt Alexander Blackman.
Blackman, aged 41, was jailed for life in 2013 after being convicted of shooting the wounded Afghan captive in the chest at close range in Helmand province two years before.
The rally in support of the soldier, originally from Taunton in Somerset, coincides with the anniversary of the founding of the Royal Marines.
A Ministry of Defence spokeswoman confirmed that servicemen and women were "routinely" given reminders that regulations forbid them from attending "political protests, marches, rallies or demonstrations".
"Any gathering which seeks to protest against a decision taken by the legal system or the Government falls into this category," she added.
The move has caused anger among supporters.
Rally organiser John Davies, a former marine, insisted the event did not fall into the banned categories.
Blackman was serving with Plymouth-based 42 Commando in September 2011, when he came across an Afghan insurgent who had been injured in an attack by an Apache helicopter.
Video from another marine's helmet cam showed him quoting Shakespeare before shooting the injured man in the chest with a 9mm pistol.
He then said: "There you are. Shuffle off this mortal coil, you c***. It's nothing you wouldn't do to us", turning to his comrades and adding: "Obviously this doesn't go anywhere, fellas. I just broke the Geneva Convention."
At trial, he denied murder, claiming he believed the man was already dead and that he had been taking out his anger on a corpse.
An appeal against his conviction was rejected by the Court Martial Court of Appeal, but his minimum sentence was reduced to eight years to reflect the combat stress disorder he had been diagnosed with.
Blackman has since spoken of his anger, claiming he was made a "scapegoat".
An online petition calling for his conviction to be quashed gained more than 100,000 signatures last year.