The commission has written to Mr Hide telling him the jacket, which has a small party logo and slogan on the pocket, might constitute an "election advertisement" under the Electoral Finance Act and therefore require an authorising statement.
But Mr Hide today said he intended to ignore the "ridiculous" letter.
"This is the stupidity of life under Helen Clark. You get told what jacket you can wear. Next she'll be telling me what underwear I can wear," he told NZPA.
"I just reject the fact that Kiwis went and fought and died for free speech and now we've got a government that tells us that you can't wear a fashionable jacket that's got a wee label on it saying ACT. Even Mugabe wouldn't try that on."
Mr Hide bought the $1300 jacket in July, partly with the intention of testing the Act. It carries the ACT party slogan "the guts to do what's right".
Mr Hide said the Electoral Commission letter was sparked by a query in July.
The complainant wrote to the commission and provided a newspaper article about the jacket and pictures of Mr Hide wearing it.
"On the basis of the information supplied, it appears that the item may be an election advertisement, and if it is an election advertisement, it may not fully comply with these provisions," the letter says.
Under the Electoral Finance Act, "published election advertisements", must carry the authorisation of the party's financial agent.
The Act was passed last year by Labour with the support of New Zealand First, the Greens and the Progressive Party.
National has said it will repeal the Act.
Under its provisions, if there was a finding of "illegal practice", Mr Hide could be fined $10,000 and ACT's financial agent $40,000.