Scenic view of Dean Village in Edinburgh. Credit: Michela Sieman/Travel + Leisure The United Kingdom has started strictly enforcing its Electronic Travel Authorisation (ETA), turning away travelers without the digital form. The UK first rolled out the program for the large majority of countries last year, including for travelers from the United States. However, the UK said it started strictly enforcing the ETA on Feb. 25, requiring airlines to deny boarding to passengers who don't have a valid ETA, eVisa, or other valid documentation, according to the government. "The ETA scheme is a vital part of our work to strengthen the UK’s border security, helping to deliver a more efficient and modern service that works for both visitors and the British public," Mike Tapp, the UK's minister for migration and citizenship, said in a statement.…