No Doubt's Tony Kanal TRO Against Trespasser Who Believes Heath Ledger is Still There

One of Gwen Stefani's bandmates claims he's having some trouble with a fella who thinks Heath Ledger is still kicking and living on his property -- and he's asked a judge for help.

No Doubt bassist Tony Kanal filed for and received a temporary restraining order against a guy named George Leonardopoulos ... whom Kanal says has terrorized his family for the past few months with unannounced and unwelcome visits.

According to the docs, obtained by TMZ, Kanal claims Leonardopoulos has swung by his L.A.-area pad repeatedly since late January -- even hopping a gate onto the property on one occasion.

On one such alleged drop-in from just last week ... Kanal claims Leonardopoulos came to their front gate and buzzed the intercom, telling Kanal's wife that he used to live there with the previous owner of the property -- and that person is Heath.

Kanal says he purchased the house from HL in 2005 (before the actor's death) and Leonardopoulos apparently lived at the house in the past and bizarrely told the Kanals he thinks Heath is still on the premises ... and alive.

Even creepier ... Leonardopoulos allegedly said it was gravely important he be let in to pop into their garage so he could "wake" Heath -- telling them if "you know what is good for you, you will let me in." At least that's what Kanal is claiming here in his TRO paperwork.

In addition to the alleged threats, Kanal says they've seen Leonardopoulos wielding a large stick and a knife and that they've called the cops on him in the past. Now, they're asking for legal help in the form of a restraining order ... and they got it.

A judge signed off on Friday, and it's in effect until a hearing can be held later this month. Leonardopoulos has to stay 100 yards from the Kanal family and their grounds until this can be hashed out.