Peaceful picketing at or near a person's own place of work for the purpose of obtaining or communicating information, or persuading others not to work, is lawful if it is in contemplation of furtherance of a trade dispute. However, this does not give the right to contravene byelaws made in pursuance of a power conferred by statute, holds the High Court in British Airports Authority v Ashton and others.
In MacShane and Ashton v Express Newspapers Ltd [1980] IRLR 35 HL, the House of Lords held that the Court of Appeal had erred in granting an interlocutory injunction restraining the defendants from instructing NUJ members employed on national newspapers to "black" copy from the Press Association.
In JE Broome v Director of Public Prosecutions [1974] IRLR 26 HL, the House of Lords held that the appellant had no authority or excuse under the Industrial Relations Act, section 134 for willfully obstructing free passage along the highway contrary to the Highways Act, section 121.
In Secretary of State for Employment v ASLEF (No 2) [1972] 2 All ER 949 CA, the Court of Appeal held that works rules or job descriptions are not of themselves contractual. They are guides as to the way in which work should be performed and should be interpreted in a reasonable way. If interpreted in an unreasonable way in order to disrupt employment this will be breach of contract.