The UK is expected to face additional legal challenges in relation to its permanence in the single market in a post-Brexit scenario, as reported by Open Britain (a cross-party campaign for the best deal with Europe).

Should the UK leave the customs union, businesses who are actively involved into importing and exporting goods are expected to be forced to cope with a significantly increased amount of bureaucracy and paperwork as a result of UK's departure from the EU.

The EU customs union provides that unified tariffs are levied on imports across Europe. This implies no additional charges and paperwork. According to the data provided by Open Britain, should the amount of imports and exports remain unchanged, businesses would have to complete more than 45m import declaration and 15m export declarations every year.

The estimate clashes with the pro-Brexit argument that leaving the EU would have resulted into less bureaucracy and paperwork for businesses operating import and export operation across Europe. The group has also urged the government to draft a cost-benefit analysis of leaving the customs union rather than merely (and inaccurately) stating that the measure would benefit UK businesses.

However, as the Supreme Courts is still expected to consider the Article 50 Legal Challenge, a new case relating to the necessity of triggering another legal measure in order to leave the single market is brought to the court.

The government is believed to have no mandate to withdraw from the single market, as it was not included in the Conservative party's manifesto and in the ballot paper on June 23rd. Moreover, it has been suggested that Article 127 of the EEA would have to be triggered.

Dominic Grieve, the former attorney general, has nonetheless casted doubts on the legal basis of the new challenge, claiming the process of leaving the single market might not be separated from the departure from the EU.

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