Uganda's President Yoweri Museveni has signed into law an amendment that will allow, once again, civilians to be tried in a military court under certain circumstances.

A previous law permitting such trials was ruled unconstitutional by the Supreme Court in January.

Before that ruling, civilians could be taken to a military tribunal if they had been found with military equipment like guns or army uniforms. Activists had complained that the law was used to persecute government critics.

Parliamentarians passed the amendment last month amid a heavy police presence and a boycott by opposition lawmakers, who argued that it violated the ruling by the country's highest court.

In January, the judges said that the military courts were neither impartial nor competent to exercise judicial functions, the International Society for Human Rights reported at the time.

The amendment appears to try and address some of the issues.

It says that those presiding over the tribunals should have relevant legal qualifications and training. It also says that while performing their legal functions they should be independent and impartial.

For years, activists had argued that the military courts were being used by the government to silence opponents.

A recent high-profile case followed November's arrest of long-time opposition leader Kizza Besigye. He was picked up in neighbouring Kenya, taken across the border and then charged in a military court with possession of pistols and attempting to purchase weapons abroad, which he denied.

Those charges were dropped when his case was transferred to a civilian court following the Supreme Court ruling.

Museveni, who has been in power since 1986, previously defended the use of military courts saying that they dealt with the "rampant activities of criminals and terrorists that were using guns to kill people indiscriminately".

He said that civilian courts were too busy to "handle these gun-wielding criminals quickly".