Former professional fighter and boxing promoter, David Letizia, allegedly installed a bunker containing "an arsenal of very high-powered firearms being incorrectly stored", police said in a statement.

The bunker in High Wycombe, near Perth airport, was found after a tip-off led police to the storage unit in 2022, which was hidden from sight by a hydraulically lifted couch.

But under current state laws, Letizia largely escaped punishment, WA police minister Paul Papalia said.

The Perth-based man will face court again later this year, but has pleaded guilty to multiple firearms charges and was fined $3,200, according to police.

"Unbelievably, the worst offence this individual has allegedly committed is failing to apply to the local council for approval to build the bunker and underground shooting range," Mr Papalia said.

"Our laws are outdated," Mr Papalia said.

"They allow some very high-powered firearms that really are designed for shooting rhinos or penetrating armour plating," he said.

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Mr Papalia said there is no justification for owning those weapons and the state government planned to ban them from July 1, 2023.

The WA government will offer market-value to buy back 56 types of firearms, including long range weapons with "extraordinary power and precision".

Investigations by WA police found almost half of the state's deaths were connected to the poor mental health of the gunperson.

In the past six months, 46 firearm licences were revoked based on mental illness, WA police said in a statement.