Whether new legislation is introduced, or existing powers used, it is very likely that multiple consultation processes would be required to implement the above. This presents an opportunity for interested parties, such as delivery companies or businesses who would be affected by the plans, to raise objections. Outside London, it has often proven difficult to obtain public support for proposals that restrict traffic, as evidenced by resistance to the Greater Manchester Clean Air Zone charging scheme and York City Council's failed attempt to impose restrictions in relation to Lendal Bridge and Coppergate.

Beyond public consultations, both before and after the passing of any enactments, the exercise of any powers referred to above are subject to challenge in the courts through judicial review and will have to be used in a way that allows the user of the power to demonstrate that it has not acted in a way whereby its exercise of the power:

The Postal Services (Universal Postal Services) Order 2012 (the Order) contains a description of the services that Ofcom considers should be provided in the UK as part of the universal postal service, and the standards with which those services need to comply. Article 4 of the Order sets out to where the postal package is to be delivered. This article essentially requires postal packages to be delivered to the address on the postal package unless the addressee has requested that the postal package is delivered elsewhere. Although Article 4 permits Ofcom to approve different delivery addresses, this power is only intended to be used in exceptional circumstances. The requirement to deliver goods to the CUCC would be in breach of Royal Mail's obligations as Universal Service Provider. Given the wide definition of postal services, even if letters and small parcels are excluded from the requirement to be delivered to the CUCC, there would be a reasonable argument that Royal Mail's Universal Service Provider obligations could not be complied with and as such the requirement to deliver to a CUCC could be challenged for being ultra vires, illegal and/or irrational. Therefore, in order to require the Royal Mail to deliver to the CUCC, it is likely that legislation relating to the Universal Postal Services would need to be amended or repealed.

There are further potential grounds of challenge under particular pieces of legislation. Depending upon how a CUCC was implemented and the reasons for such implementation, there would be a reasonable argument that the above proposals were a breach of the Human Rights Act 1998 in that the delivery to a CUCC, and either collection from the CUCC, or potential delay in delivery from the CUCC, could interfere with peaceful enjoyment of a person's possessions, which could include goods being sent or received, possessions used by a delivery business and even shares in a business affected by the above proposals. Any interference would have to be within the general interest and a fair balance struck between that and the rights of the owners of property. If found in breach, the claimant could receive an award of damages and incompatible legislation could be declared incompatible with the Human Rights Act 1998 or, in the case of secondary legislation, struck down.

The Equality Act 2010 could also provide a route of challenge. Any person exercising a public function or providing a service to the public must not discriminate when doing so, which can include indirect discrimination against people with protected characteristics (including perhaps of particular relevance in this case disability and religion or belief). It would be plausible that, on the assumption the implementation of a CUCC slowed down deliveries/collections, there would be scope, for instance, for arguments that the scheme was discriminatory. It would then fall to the public authority to argue that the discrimination was for a legitimate aim, such as perhaps reducing air pollution or protecting an area from damage, and the claim would therefore turn on whether the means were proportionate to the aim. In addition, there is a duty on public bodies to make reasonable adjustments to avoid disadvantage caused to disabled people. In the case of the CUCC, this could mean that goods to be delivered to certain people may need to be excluded from the requirement to be delivered to the CUCC. If the Equality Act 2010 is breached, the claimant may be entitled to an injunction, which could compel the authority to do or refrain from doing something, or to an award of damages.