Who identifies when only transnational legislation will do?

When inviting bids it's normal (I hope) that buyers carry out a risk assessment, identify who is best placed to manage those risks and stipulate the insurance cover which the successful provider will have to put in place during delivery of the contract.

The insurance cover aims to protect the buyer and others who may suffer during the supplier's delivery of the contract.  On one hand the buyer is being protected through the insurance in the event of supplier failing to deliver or causing damage.  On the other hand