Picketing will only be lawful if it is carried out in contemplation or furtherance of a trade dispute and its purpose is to peacefully obtain or communicate information or to peacefully persuade any person to work or to abstain from working. Any action which goes beyond this will not be classed as lawful picketing and will expose the union which has organised the action to potentially liability.
In general, picketing must be carried out at or near the place where the employer works or carries on business. The picketing of an employer other than the one directly involved in the dispute is lawful and protected so long as it complies with the standard requirements in relation to picketing and the picketers reasonably believe, at all times, that the subject of the secondary picketing directly assisted the employer in frustrating the strike or other industrial action.
Where a trade union authorises or endorses industrial action and immunity is lost for whatever reason, anyone who suffers loss as a result of the action (such as employers or customers of the employers) has a right to certain remedies. The remedy most commonly sought is a High Court injunction requiring the union to withdraw that authorisation and to ensure that its members are not induced to take part in industrial action. Damages for the loss suffered may also be sought.
Where a trade union authorises industrial action, the employer may seek an injunction against that union to prevent, for example, a picket from continuing. Trade unions, however, are protected against the grant of interim or interlocutory injunctions provided that, among other things, they have held a ballot prior to the action starting. The rules on what comprises an effective ballot for these purposes must be strictly adhered to.