Parties to contracts with a term that will extend beyond the date of the exit would be well advised to consider whether the consequences of Brexit will affect the operation or performance of their contracts. For example, if in practice a contract can only be performed because of some feature of EU law, such as free movement of goods, then a result of the UK leaving the EU may be that the contract is frustrated or performance excused because of its force majeure provisions.
Alternatively, one of the parties may find that the contract can be performed but (for example because of import duties which are imposed following Brexit) it is no longer profitable for it. In such event it is likely to want to look for some means of terminating the contract or suspending performance and so will need to analyse whether the force majeure provisions in the contract allow it to suspend performance and eventually terminate the contract. The other party to the contract may well take a different view on whether Brexit constitutes a force majeure event.
Such issues are bound to lead to disputes and in order to pre-empt them parties should review their contractual arrangements in order to assess whether Brexit is likely to have unplanned (and undesired) consequences for each contract.