The plan was released on Wednesday for comment.

Currently the Parks and Conservation service must apply to the Conservator of Flora and Fauna for a licence for the annual cull - and the licence can be appealed, an avenue for challenge that has tied up authorities in court cases most years since the cull began in 2009.

In 2015, the government issued a two-year licence, with the result that the 2016 cull went ahead without a challenge. Now it proposes getting rid of the need for a licence altogether. This week, the minister declared kangaroos a "controlled species", which allows the cull to go ahead without a licence.

The government says Parks and Conservation will still seek approval each year from the conservator, setting out how many kangaroos are to be shot and in which reserves.

Animal Liberation ACT's Carolyn Drew said the move was simply a way to forestall any legal challenges, but she would be looking closely to see what court avenues remained.

"They may think they've got the game sewn up but often they make mistakes, especially when they rush things through .. and we'll certainly be sniffing those down with legal assistance," she said.

Ms Drew said when the government changed the Nature Conservation Act in 2014 to allow native animals to be declared a "controlled species", "we knew that it was harbinger of something but we weren't sure what they were up to - it's a bit like a mad chess match sometimes."

"We knew something was in the offing and I said there and then this just simply make it easier for them to kill the kangaroos. Now we know."

The new management plan envisages shooting kangaroos each year to maintain them at a density of about one per hectare on grassland - and less in woodland and forest. In open woodland, the density is 0.9 kangaroos a hectare, in woodland 0.5 kangaroos a hectare and in open forest and other forest the density will be just 0.1 kangaroos a hectare. Numbers are much higher on many reserves.

Each year, the aim is to bring kangaroo numbers back to a density below the target at cull time, so that the average density in the year to follow before the next cull remains at the target figure.

The government has been shooting kangaroos in an annual cull since 2009, despite vehement opposition from activists.

Over eight years, government shooters have culled 12,271 kangaroos on reserves, and in the past three years they have killed another 2061 pouch young.

Last year's was the biggest cull since 2011, with 1989 animals shot and another 800 pouch young killed.

Each year since 1997, the government has also issued licences to allow kangaroos on rural land to be culled. In 2015, 80 rural properties were licensed to cull 20,722 kangaroos. They reported shooting 11,130. It was the biggest number to date.

In declaring eastern grey kangaroos a controlled native species, Mr Gentleman said he was satisfied they had an unacceptable environmental and economic impact, bringing excessive grazing pressure, degrading native grassy ecosystems, and the habitats of threatened species. They also hit the economic viability of rural properties and increased the cost of managing land.

High densities were "most likely a result of fundamental changes over time to the regulation of kangaroo abundance through predation", the declaration said, citing Aboriginal hunting of mega-fauna including large predators 40,000 to 50,000 years ago, and the dingo's arrival several thousand years ago. European settlement had suppressed the dingo and ended aboriginal hunting.

The cull ran into trouble last year when it was discovered the shooters had been using silencers illegally in the cull since 2009, having mistakenly been issued permits allowing silencers by the registrar of firearms each year, who is also the deputy chief police officer. Silencers are illegal in Canberra.

So far culling has been carried out at 14 of the 39 nature reserves in Canberra, with the government envisaging expanding the program to new reserves.