Disqualified AM Aled Roberts followed out-of-date rules
A disqualified Liberal Democrat member of the Welsh assembly was the victim of out-of-date guidance for candidates, a report has found.
Legal advice for AMs said Aled Roberts did everything reasonably expected.
He and fellow Lib Dem John Dixon stood down when it emerged they were members of bodies to which AMs cannot belong.
But the report said Mr Dixon did not check the relevant rules for candidates. Their party will try to reinstate them as AMs on Wednesday.
An investigation by Gerard Elias QC, the assembly's standards commissioner, said advice from the Electoral Commission referred Mr Roberts to outdated regulations.
Although the English-language guidance was up-to-date, Mr Roberts followed Welsh-language guidance that pointed him towards regulations on proscribed organisations from 2006. They were replaced in 2010.
The report finds Mr Roberts, a North Wales AM, "did everything that he could have reasonably been expected to do in ensuring that he was not a disqualified person for the purpose of nomination or election to the National Assembly".
Mr Dixon, who was elected an AM for South Wales Central, followed the Electoral Commission's English-language advice.
Although he acknowledged he had a responsibility to read the 2006 and 2010 order "he further acknowledges that at no time did he check the order (either in its 2006 or 2010 form)".
"Perhaps because he was lulled into a false sense of security by his experiences in earlier elections, he honestly believed that he was eligible to be a member of the National Assembly," the report says.
The Lib Dems have tabled motions in the assembly to reinstate the two on Wednesday.
Following rumours the votes could be delayed, Plaid Cymru AM Simon Thomas said on Twitter: "If we don't sort this out this week then the returning officers should step in. Farce has gone on long enough."
The Electoral Commission said it would not comment until after AMs had voted.
A spokesperson for the Welsh Language Board said: "The case highlights a possible failure to conform to a language scheme. The board is looking into the matter."
The two Lib Dems were told they would not face charges last month following a police investigation into a complaint by United Kingdom Independence Party MEP John Bufton.
They were disqualified after it emerged Mr Dixon was still a member of the Care Council for Wales, which regulates social care workers. Mr Roberts was a member of the Valuation Tribunal for Wales, which deals with appeals about business rates and council tax.