As a general matter, law professors do not have to teach during the summer. Indeed, we barely teach during the academic year, as compared to virtually all other academic disciplines. The standard load is two lectures classes, plus a small seminar. The only way universities can attract elite faculty to teach in the summer is to situate the classes in exotic locations. Professors, and their families, have most-expenses-paid vacations to foreign cities. Sure, there are a few hours of teaching in the morning. But the rest of the time is free. And those same classes could easily be taught at the home institution. But again, professors would never sacrifice their summer breaks to teach domestically. What about students? Most law schools offer summer classes on this side of the pond. (I took CrimPro and a privacy law seminar during my 1L summer.) But who wants to toil in the heat? It's far more fun to study some esoteric topic in Europe.
Everyone knows these facts. It is not a secret. Indeed, over my career, I've challenged law professors who teach abroad. They insist that these programs are rigorous. So are classes in the United States. They insist that students can build camaraderie. They can do that here as well. They insist that students can be exposed to faculty who do not teach at our institution. Well, now Zoom can do that quite well. Plus, it pains me that students take on more debt to pay for cushy vacations, rather than trying to earn an actual salary over the summer. If I am reviewing a resume, and I see a summer-abroad program, I immediately think the person made a poor decision of how to spend the 2L summer.
I'm sure I'm an outlier. Plenty of professors who benefit from these programs love them. Same for administrators who tag along on the trips! Plus all students love vacations with academic credit. Rant over.