2/ This may sound unsettling to Brexiteers, but it turns out the UK agreed to this in the Withdrawal Agreement. Article 12(4) of the Protocol: "In particular, the Court of Justice of the European Union shall have the jurisdiction provided for in the Treaties in this respect.
In an interview with @rtenews Ms von der Leyen said: “Of course there will be checks between NI + Great Britain as it is written down in the Withdrawal Agreement. The checks will be done by the Brits under the supervision of the European Union and the European Court of Justice.”
Immediate response from Tusk - ' Withdrawal agreement is and remains the best and only way to ensure an orderly withdrawal of the United Kingdom from the European Union. The backstop is part of the Withdrawal Agreement, and the Withdrawal Agreement is not open for re-negotiation'