Expired tube of toothpaste and Malala Yousafzai memoir also among cell items that led to US soldier being allegedly charged with four violations of custody rules, lawyers say

Chelsea Manning, the US army soldier serving a 35-year military prison sentence for leaking official secrets, has been threatened with indefinite solitary confinement for having an expired tube of toothpaste in her cell and being found in possession of the Caitlyn Jenner Vanity Fair issue, according to her lawyers and supporters.

Manning, a Guardian columnist who writes about global affairs, intelligence issues and transgender rights from prison in the brig of Fort Leavenworth, Kansas, has allegedly been charged with four violations of custody rules that her lawyers have denounced as absurd and a form of harassment. The army private is reportedly accused of having showed “disrespect”; of having displayed “disorderly conduct” by sweeping food onto the floor during dinner chow; of having kept “prohibited property” – that is books and magazines – in her cell; and of having committing “medicine misuse”, referring to the tube of toothpaste, according to Manning’s supporters.

The maximum punishment for such offences is an indeterminate amount of time in a solitary confinement cell.

The fourth charge, “medicine misuse”, follows an inspection of Manning’s cell on 9 July during which a tube of anti-cavity toothpaste was found. The prison authorities noted that Manning was entitled to have the toothpaste in her cell, but is penalizing her because it was “past its expiration date of 9 April 2015”.

The “prohibited property” charge relates to a number of books and magazines that were found in her cell and confiscated. They included the memoir I Am Malala by Nobel peace prize laureate Malala Yousafzai, a novel featuring trans women called A Safe Girl to Love, the LGBT publication Out Magazine, the Caitlyn Jenner issue of Vanity Fair and a copy of Cosmopolitan that included an interview with Manning.

Also confiscated was the US Senate report on torture. It is not clear why any of these publications were considered violations of prison rules – a request by the Guardian to the army public affairs team for an explanation of the charges received no immediate response.

Nancy Hollander, the lawyer dealing with Manning’s appeal against the 35-year sentence for being the source of the WikiLeaks disclosures of US state secrets, called the charge relating to an expired tube of toothpaste “utterly ridiculous”. She added: “I’m concerned that books have been taken from her – those books came to her legally and are clearly not a security threat.”

Hollander also had objections to the fact that the details of the charges listed by Fort Leavenworth included a reference to Manning saying “I want my lawyer” following a discussion with a prison officer. “To ask for a lawyer when you are being accused of something by a prison officer – that’s not ‘disrespect’,” Hollander said.

Chase Strangio, a staff attorney with the ACLU who is handling Manning’s legal dispute with the US military over her health treatment in prison as a transgender woman, said the charges were very concerning. “They could chill her activities or even silence her altogether.”

Strangio said it seemed that Manning was being unfairly targeted. “Chelsea has a growing voice in the public discussion and it would not surprise me were these charges connected to who she is.”

Strangio is in possession of legal documents that were issued by the US military in pre-charging proceedings. The actual charges were read out by Manning verbatim to her supporters, who then published the wording in a petition that has been set up calling for the charges to be dropped. A disciplinary hearing is scheduled for 18 August; should it go ahead the petitioners demand that it should be made open to the public.