Election poster laws are invalid because they interfere with Australians' constitutional right to communicate on political matters, a former MP has told a court.
Former United Australia Party federal MP Craig Kelly is accused of doing "public harm" by displaying UAP posters before May's federal election that did not properly display required details.
Those details - including the name of the person or party authorising the poster - were absent or illegible, the Australian Electoral Commission says.
But Mr Kelly says his posters used the same font and format for the authorisation as the posters from prior elections when he was a Liberal Party member.
In his defence filed with the Federal Court and released on Tuesday, Mr Kelly says the commission raised concerns about his posters prior to the election but "failed and/or refused" to tell him what an acceptable font would be.
He argues the relevant electoral laws burdened the implied constitutional freedom of political communication by requiring the inclusion of the particulars - "the format of which is subjective, undefined or ambiguous".
The inexact nature of the requirements disabled candidates and political parties from complying with them.
"The burden on the freedom is not justified," his defence says.
He also denies being the notifying candidate behind the offending posters, claiming "many" posters were stolen in the lead-up to the election and were not approved by him.
The case returns to the Federal Court on October 20. A hearing this week was cancelled so Mr Kelly could file a document putting federal and state governments on notice of his constitutional claim.
The allegedly offending posters had the UAP candidate's portrait and the words "our local MP" and were displayed outside train stations and near pre-poll centres in the Hughes electorate in southern Sydney.
"Persons who saw the posters in the community would not be able to read the particulars required by the Electoral Act without carefully scrutinising the signs at a very short distance, or at all," the commission's claim says.
The commission is seeking civil penalties and its legal costs be paid by Mr Kelly.
On the eve of the election, the commission tried and failed to have a court force Mr Kelly to remove the allegedly defective signage before polls opened.
Mr Kelly failed to win a fifth term as the member for Hughes, after defecting from the Liberal Party to the Clive Palmer-bankrolled UAP in 2021.
The former furniture salesman came under increased scrutiny during the pandemic after being criticised for spreading misinformation about vaccines and alternate coronavirus treatments on social media, and accused by the Therapeutic Goods Administration of misrepresenting its data on vaccine reactions.