you are a helpful assistant, briefly summarise this news article:

Police Scotland is planning to introduce a new clean-shaven policy for frontline officers, according to correspondence seen by the BBC.

It means hundreds of officers will have to shave off their beards and moustaches by the end of the month.

Four are understood to be taking legal action in relation to the policy.

Police Scotland said it was necessary so officers and staff could wear protective FFP3 masks which require users to be clean-shaven.

The policy, which also covers civilian staff in frontline roles, has been approved by the chief constable and is due to be introduced on 29 May.

During the Covid pandemic police officers were fitted with specialist masks designed to protect them from the virus.

A message posted on Police Scotland's internal website from Assistant Chief NAME_1 said lessons learned from the pandemic identified that FFP3 masks offered the most appropriate and effective respiratory protection to officers and staff.

He said that while the risk from coronavirus had lowered, wider risks remained to officers and staff attending calls such as fires, road accidents and chemical incidents which required PPE (personal protective equipment) to be worn.

Police Scotland's new respiratory protective equipment (RPE) policy will mean that where it can be "reasonably foreseen" that any officer or member of staff will use an FFP3 mask they should be clean-shaven.

This includes all local policing frontline officers, NAME_2