EU law still stands in the UK until it ceases being a member. Whist UK remains a member it must abide by all EU treaties, laws and regulations and laws, but will not be able to take part or have any inflence in any decision-making at all.

Article 50 will need to be formally invoked, the UK will then have a countdown of two years to negotiate its withdrawal.
Mrs May has stated she will not invoke Article 50 before the end of 2016

Looks like in 2018 UK will be EU-free