What type of body is the employer?
The situation is simple when it comes to public bodies - the Scottish Independence Referendum Act 2013 imposes restrictions on the publication of material by public bodies in the 28 days before the Referendum. If the employer is a public body then this would apply.
So what about private sector organisations? What happens if employees attend work wearing Yes badges (or, just as likely, No Thanks badges) and spend much of their time criticising the opposing view. What can an employer do? We live in a democracy where we have the right to freedom of thought, conscience and religion. Such fundamental freedoms can only be restricted by domestic legislation in order to protect the rights of others. The Equality Act 2010 provides protection to those expressing a "philosophical belief". In principle a political belief can amount to a philosophical belief (Grainger Plc & Ors v. Nicholson ). However there have also been a number of cases involving BNP members in which it was found that their beliefs did not qualify as philosophical ones (Baggs v Fudge  and Finnon v Asda Stores Ltd ). Whether the employee's belief is covered might well depend on the individual employee and their own circumstances. The fact is though that neither an employee nor an employer will be likely to want to go to an Employment Tribunal to have the strength of belief analysed in such detail. The issue is a short-term one, lasting only until next week, after which we can all return to our normal day to day activities.
Can an employer do anything or are they stuck with this?
An employer can, of course, objectively justify a restriction on people expressing their views in a way which others might find intimidating or offensive. Whilst protections are in place in relation to one particular belief, those protections are equally in place for the opposing (or different) beliefs. When similar types of claim (in the context of religious belief) came before the European Court in 2013 in the case Eweida and others v United Kingdom, the European Court of Human Rights considered four Christian employees' arguments that UK law failed adequately to protect their right under the European Convention on Human Rights to manifest their religious beliefs. Two of those complaints related to the wearing of a crucifix at work. The other two related to Christians refusing to conduct parts of their roles because it would involve providing marriage/counselling services to same-sex couples. Only one of the four employees was successful. The other three employers successfully justified a restriction on religious expression on the basis of health and safety (re the crucifix) and achieving the legitimate aim of providing an equal service to all (re same-sex marriage/counselling).
Therefore, if the displaying of a Referendum opinion is such that it is creating an environment which is intimidating, hostile or offensive, an employer may well wish to take action. It would be a legitimate aim to wish to preserve dignity at work for all. It would also be a legitimate aim to prevent bullying and harassment in the workplace. If campaign paraphernalia is being used in a way which concerns other employees, then an employer would be able to argue that a ban on campaign paraphernalia in the workplace is a proportionate means of achieving that legitimate aim. The employer should consider first whether or not there is a different solution, but having done that, it may decide that the most effective one is a ban.