Muggles can still cause the magic to work in some of them.
Enchanted objects falling into the hands of Muggles and displaying magic while in Muggle ownership is the reason that the Ministry has a Misuse of Muggle Artefacts Office.
“He works in the most boring department,’ said Ron. ‘The Misuse of Muggle Artefacts Office.’
‘It’s all to do with bewitching things that are Muggle-made, you know, in case they end up back in a Muggle shop or house. Like, last year, some old witch died and her tea set was sold to an antiques shop. This Muggle woman bought it, took it home and tried to serve her friends tea in it. It was a nightmare – Dad was working overtime for weeks.’
‘The teapot went berserk and squirted boiling tea all over the place and one man ended up in hospital with the sugar tongs clamped to his nose. Dad was going frantic, it’s only him and an old warlock called Perkins in the office, and they had to do Memory Charms and all sorts to cover it up …” - Harry Potter and the Chamber of Secrets, Chapter 3 (The Burrow)
Flying carpets are considered a "Muggle Artefact" so a Muggle could likely "use" them.
Arthur Weasley explains to Barty Crouch Sr. that flying carpets would be banned under the law preventing wizards from enchanting Muggle objects.
“Oh, and I’ve been wanting a word with you, too, Arthur,’ said Mr Crouch, his sharp eyes falling upon Mr Weasley. ‘Ali Bashir’s on the warpath. He wants a word with you about your embargo on flying carpets.’
Mr Weasley heaved a deep sigh. ‘I sent him an owl about that just last week. If I’ve told him once I’ve told him a hundred times: carpets are defined as a Muggle Artefact by the Registry of Proscribed Charmable Objects, but will he listen?” - Harry Potter and the Goblet of Fire, Chapter 7 (Bagman and Crouch)