I visited Guam back in 2014 to empty my UA miles as China-Guam used to be a sweet spot for UA miles redemption back then. I actually got trouble entering Guam

I visited Guam back in 2014 to empty my UA miles as China-Guam used to be a sweet spot for UA miles redemption back then. I actually got trouble entering Guam because back then I was on L1 visa, which only allows me to enter the US for work, and my employer does not have any office at Guam and I don't have a connection from Guam to US mainland. After being held at the airport for hours (I believe they called my hotel for verification) they finally stamped a parole on my passport and let me in.